From: Viresh Kumar <viresh.kumar@linaro.org>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Jan Kara <jack@suse.cz>, Tejun Heo <tj@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
vlevenetz@mm-sol.com, vaibhav.hiremath@linaro.org,
alex.elder@linaro.org, johan@kernel.org,
akpm@linux-foundation.org, rostedt@goodmis.org
Subject: Re: [Query] Preemption (hogging) of the work handler
Date: Tue, 12 Jul 2016 07:12:18 -0700 [thread overview]
Message-ID: <20160712141218.GT4695@ubuntu> (raw)
In-Reply-To: <20160712140300.GA520@swordfish>
[-- Attachment #1: Type: text/plain, Size: 967 bytes --]
Hi Sergey,
On 12-07-16, 23:03, Sergey Senozhatsky wrote:
> Thanks, Petr.
>
>
> so, I'm looking at this thing now:
Thanks. Though just to mention, I have seen this only once yet :)
> : [ 12.874909] sched: RT throttling activated for rt_rq ffffffc0ac13fcd0 (cpu 0)
> : [ 12.874909] potential CPU hogs:
> : [ 12.874909] printk (292)
>
> so it's either cond_resched() does not reshed, keeping printk kthread
> active, which, however, upsets the sched and triggers throttling (umm, what);
>
> or we, somehow, have `console_may_schedule == 0' in this final console_unlock(),
> so cond_resched() never happens.
>
> I'm looking at mainline 3.10, tho.
My setup currently looks like this:
- 3.10
- + all printk patches from 3.10 to mainline
- + your patches
- Attaching my printk.c, so you can see the current state.
> Viresh, can you verify if we can do cond_resched() from console_unlock()
> (console_may_schedule != 0) ?
I will try that today.
--
viresh
[-- Attachment #2: printk.c --]
[-- Type: text/x-csrc, Size: 88106 bytes --]
/*
* linux/kernel/printk.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* Modified to make sys_syslog() more flexible: added commands to
* return the last 4k of kernel messages, regardless of whether
* they've been read or not. Added option to suppress kernel printk's
* to the console. Added hook for sending the console messages
* elsewhere, in preparation for a serial line console (someday).
* Ted Ts'o, 2/11/93.
* Modified for sysctl support, 1/8/97, Chris Horn.
* Fixed SMP synchronization, 08/08/99, Manfred Spraul
* manfred@colorfullife.com
* Rewrote bits to get rid of console_lock
* 01Mar01 Andrew Morton
*/
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/console.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/nmi.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/security.h>
#include <linux/bootmem.h>
#include <linux/memblock.h>
#include <linux/aio.h>
#include <linux/syscalls.h>
#include <linux/kexec.h>
#include <linux/kdb.h>
#include <linux/ratelimit.h>
#include <linux/kmsg_dump.h>
#include <linux/syslog.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/rculist.h>
#include <linux/poll.h>
#include <linux/irq_work.h>
#include <linux/utsname.h>
#include <linux/ctype.h>
#include <linux/uio.h>
#include <linux/kthread.h>
#include <linux/sched/rt.h>
#include <asm/uaccess.h>
#include <asm-generic/sections.h>
#define CREATE_TRACE_POINTS
#include <trace/events/printk.h>
#include "console_cmdline.h"
#include "braille.h"
#include "internal.h"
#ifdef CONFIG_EARLY_PRINTK_DIRECT
extern void printascii(char *);
#endif
int console_printk[4] = {
CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
};
/*
* Low level drivers may need that to know if they can schedule in
* their unblank() callback or not. So let's export it.
*/
int oops_in_progress;
EXPORT_SYMBOL(oops_in_progress);
/*
* console_sem protects the console_drivers list, and also
* provides serialisation for access to the entire console
* driver system.
*/
static DEFINE_SEMAPHORE(console_sem);
struct console *console_drivers;
EXPORT_SYMBOL_GPL(console_drivers);
#ifdef CONFIG_LOCKDEP
static struct lockdep_map console_lock_dep_map = {
.name = "console_lock"
};
#endif
/*
* Number of registered extended console drivers.
*
* If extended consoles are present, in-kernel cont reassembly is disabled
* and each fragment is stored as a separate log entry with proper
* continuation flag so that every emitted message has full metadata. This
* doesn't change the result for regular consoles or /proc/kmsg. For
* /dev/kmsg, as long as the reader concatenates messages according to
* consecutive continuation flags, the end result should be the same too.
*/
static int nr_ext_console_drivers;
/*
* Helper macros to handle lockdep when locking/unlocking console_sem. We use
* macros instead of functions so that _RET_IP_ contains useful information.
*/
#define down_console_sem() do { \
down(&console_sem);\
mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
} while (0)
static int __down_trylock_console_sem(unsigned long ip)
{
if (down_trylock(&console_sem))
return 1;
mutex_acquire(&console_lock_dep_map, 0, 1, ip);
return 0;
}
#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
#define up_console_sem() do { \
mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
up(&console_sem);\
} while (0)
/*
* This is used for debugging the mess that is the VT code by
* keeping track if we have the console semaphore held. It's
* definitely not the perfect debug tool (we don't know if _WE_
* hold it and are racing, but it helps tracking those weird code
* paths in the console code where we end up in places I want
* locked without the console sempahore held).
*/
static int console_locked, console_suspended;
/*
* If exclusive_console is non-NULL then only this console is to be printed to.
*/
static struct console *exclusive_console;
/*
* Array of consoles built from command line options (console=)
*/
#define MAX_CMDLINECONSOLES 8
static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
static int selected_console = -1;
static int preferred_console = -1;
int console_set_on_cmdline;
EXPORT_SYMBOL(console_set_on_cmdline);
/* Flag: console code may call schedule() */
static int console_may_schedule;
/*
* The printk log buffer consists of a chain of concatenated variable
* length records. Every record starts with a record header, containing
* the overall length of the record.
*
* The heads to the first and last entry in the buffer, as well as the
* sequence numbers of these entries are maintained when messages are
* stored.
*
* If the heads indicate available messages, the length in the header
* tells the start next message. A length == 0 for the next message
* indicates a wrap-around to the beginning of the buffer.
*
* Every record carries the monotonic timestamp in microseconds, as well as
* the standard userspace syslog level and syslog facility. The usual
* kernel messages use LOG_KERN; userspace-injected messages always carry
* a matching syslog facility, by default LOG_USER. The origin of every
* message can be reliably determined that way.
*
* The human readable log message directly follows the message header. The
* length of the message text is stored in the header, the stored message
* is not terminated.
*
* Optionally, a message can carry a dictionary of properties (key/value pairs),
* to provide userspace with a machine-readable message context.
*
* Examples for well-defined, commonly used property names are:
* DEVICE=b12:8 device identifier
* b12:8 block dev_t
* c127:3 char dev_t
* n8 netdev ifindex
* +sound:card0 subsystem:devname
* SUBSYSTEM=pci driver-core subsystem name
*
* Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
* follows directly after a '=' character. Every property is terminated by
* a '\0' character. The last property is not terminated.
*
* Example of a message structure:
* 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
* 0008 34 00 record is 52 bytes long
* 000a 0b 00 text is 11 bytes long
* 000c 1f 00 dictionary is 23 bytes long
* 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
* 0010 69 74 27 73 20 61 20 6c "it's a l"
* 69 6e 65 "ine"
* 001b 44 45 56 49 43 "DEVIC"
* 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
* 52 49 56 45 52 3d 62 75 "RIVER=bu"
* 67 "g"
* 0032 00 00 00 padding to next message header
*
* The 'struct printk_log' buffer header must never be directly exported to
* userspace, it is a kernel-private implementation detail that might
* need to be changed in the future, when the requirements change.
*
* /dev/kmsg exports the structured data in the following line format:
* "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
*
* Users of the export format should ignore possible additional values
* separated by ',', and find the message after the ';' character.
*
* The optional key/value pairs are attached as continuation lines starting
* with a space character and terminated by a newline. All possible
* non-prinatable characters are escaped in the "\xff" notation.
*/
enum log_flags {
LOG_NOCONS = 1, /* already flushed, do not print to console */
LOG_NEWLINE = 2, /* text ended with a newline */
LOG_PREFIX = 4, /* text started with a prefix */
LOG_CONT = 8, /* text is a fragment of a continuation line */
};
struct printk_log {
u64 ts_nsec; /* timestamp in nanoseconds */
u16 len; /* length of entire record */
u16 text_len; /* length of text buffer */
u16 dict_len; /* length of dictionary buffer */
u8 facility; /* syslog facility */
u8 flags:5; /* internal record flags */
u8 level:3; /* syslog level */
}
#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
__packed __aligned(4)
#endif
;
/*
* The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
* within the scheduler's rq lock. It must be released before calling
* console_unlock() or anything else that might wake up a process.
*/
DEFINE_RAW_SPINLOCK(logbuf_lock);
#ifdef CONFIG_PRINTK
DECLARE_WAIT_QUEUE_HEAD(log_wait);
/* the next printk record to read by syslog(READ) or /proc/kmsg */
static u64 syslog_seq;
static u32 syslog_idx;
static enum log_flags syslog_prev;
static size_t syslog_partial;
/* index and sequence number of the first record stored in the buffer */
static u64 log_first_seq;
static u32 log_first_idx;
/* index and sequence number of the next record to store in the buffer */
static u64 log_next_seq;
static u32 log_next_idx;
/* the next printk record to write to the console */
static u64 console_seq;
static u32 console_idx;
static enum log_flags console_prev;
/* the next printk record to read after the last 'clear' command */
static u64 clear_seq;
static u32 clear_idx;
#define PREFIX_MAX 32
#define LOG_LINE_MAX (1024 - PREFIX_MAX)
#define LOG_LEVEL(v) ((v) & 0x07)
#define LOG_FACILITY(v) ((v) >> 3 & 0xff)
/* record buffer */
#define LOG_ALIGN __alignof__(struct printk_log)
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
static char *log_buf = __log_buf;
static u32 log_buf_len = __LOG_BUF_LEN;
/* Control whether printing to console must be synchronous. */
static bool __read_mostly printk_sync = false;
/* Printing kthread for async printk */
static struct task_struct *printk_kthread;
/* When `true' printing thread has messages to print */
static bool printk_kthread_need_flush_console;
static inline bool can_printk_async(void)
{
return !printk_sync && printk_kthread;
}
/* Return log buffer address */
char *log_buf_addr_get(void)
{
return log_buf;
}
/* Return log buffer size */
u32 log_buf_len_get(void)
{
return log_buf_len;
}
/* human readable text of the record */
static char *log_text(const struct printk_log *msg)
{
return (char *)msg + sizeof(struct printk_log);
}
/* optional key/value pair dictionary attached to the record */
static char *log_dict(const struct printk_log *msg)
{
return (char *)msg + sizeof(struct printk_log) + msg->text_len;
}
/* get record by index; idx must point to valid msg */
static struct printk_log *log_from_idx(u32 idx)
{
struct printk_log *msg = (struct printk_log *)(log_buf + idx);
/*
* A length == 0 record is the end of buffer marker. Wrap around and
* read the message at the start of the buffer.
*/
if (!msg->len)
return (struct printk_log *)log_buf;
return msg;
}
/* get next record; idx must point to valid msg */
static u32 log_next(u32 idx)
{
struct printk_log *msg = (struct printk_log *)(log_buf + idx);
/* length == 0 indicates the end of the buffer; wrap */
/*
* A length == 0 record is the end of buffer marker. Wrap around and
* read the message at the start of the buffer as *this* one, and
* return the one after that.
*/
if (!msg->len) {
msg = (struct printk_log *)log_buf;
return msg->len;
}
return idx + msg->len;
}
/*
* Check whether there is enough free space for the given message.
*
* The same values of first_idx and next_idx mean that the buffer
* is either empty or full.
*
* If the buffer is empty, we must respect the position of the indexes.
* They cannot be reset to the beginning of the buffer.
*/
static int logbuf_has_space(u32 msg_size, bool empty)
{
u32 free;
if (log_next_idx > log_first_idx || empty)
free = max(log_buf_len - log_next_idx, log_first_idx);
else
free = log_first_idx - log_next_idx;
/*
* We need space also for an empty header that signalizes wrapping
* of the buffer.
*/
return free >= msg_size + sizeof(struct printk_log);
}
static int log_make_free_space(u32 msg_size)
{
while (log_first_seq < log_next_seq &&
!logbuf_has_space(msg_size, false)) {
/* drop old messages until we have enough contiguous space */
log_first_idx = log_next(log_first_idx);
log_first_seq++;
}
if (clear_seq < log_first_seq) {
clear_seq = log_first_seq;
clear_idx = log_first_idx;
}
/* sequence numbers are equal, so the log buffer is empty */
if (logbuf_has_space(msg_size, log_first_seq == log_next_seq))
return 0;
return -ENOMEM;
}
/* compute the message size including the padding bytes */
static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
{
u32 size;
size = sizeof(struct printk_log) + text_len + dict_len;
*pad_len = (-size) & (LOG_ALIGN - 1);
size += *pad_len;
return size;
}
/*
* Define how much of the log buffer we could take at maximum. The value
* must be greater than two. Note that only half of the buffer is available
* when the index points to the middle.
*/
#define MAX_LOG_TAKE_PART 4
static const char trunc_msg[] = "<truncated>";
static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
u16 *dict_len, u32 *pad_len)
{
/*
* The message should not take the whole buffer. Otherwise, it might
* get removed too soon.
*/
u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
if (*text_len > max_text_len)
*text_len = max_text_len;
/* enable the warning message */
*trunc_msg_len = strlen(trunc_msg);
/* disable the "dict" completely */
*dict_len = 0;
/* compute the size again, count also the warning message */
return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
}
/* insert record into the buffer, discard old ones, update heads */
static int log_store(int facility, int level,
enum log_flags flags, u64 ts_nsec,
const char *dict, u16 dict_len,
const char *text, u16 text_len)
{
struct printk_log *msg;
u32 size, pad_len;
u16 trunc_msg_len = 0;
/* number of '\0' padding bytes to next message */
size = msg_used_size(text_len, dict_len, &pad_len);
if (log_make_free_space(size)) {
/* truncate the message if it is too long for empty buffer */
size = truncate_msg(&text_len, &trunc_msg_len,
&dict_len, &pad_len);
/* survive when the log buffer is too small for trunc_msg */
if (log_make_free_space(size))
return 0;
}
if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
/*
* This message + an additional empty header does not fit
* at the end of the buffer. Add an empty header with len == 0
* to signify a wrap around.
*/
memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
log_next_idx = 0;
}
/* fill message */
msg = (struct printk_log *)(log_buf + log_next_idx);
memcpy(log_text(msg), text, text_len);
msg->text_len = text_len;
if (trunc_msg_len) {
memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
msg->text_len += trunc_msg_len;
}
memcpy(log_dict(msg), dict, dict_len);
msg->dict_len = dict_len;
msg->facility = facility;
msg->level = level & 7;
msg->flags = flags & 0x1f;
if (ts_nsec > 0)
msg->ts_nsec = ts_nsec;
else
msg->ts_nsec = local_clock();
memset(log_dict(msg) + dict_len, 0, pad_len);
msg->len = size;
/* insert message */
log_next_idx += msg->len;
log_next_seq++;
return msg->text_len;
}
int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
static int syslog_action_restricted(int type)
{
if (dmesg_restrict)
return 1;
/*
* Unless restricted, we allow "read all" and "get buffer size"
* for everybody.
*/
return type != SYSLOG_ACTION_READ_ALL &&
type != SYSLOG_ACTION_SIZE_BUFFER;
}
int check_syslog_permissions(int type, int source)
{
/*
* If this is from /proc/kmsg and we've already opened it, then we've
* already done the capabilities checks at open time.
*/
if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
goto ok;
if (syslog_action_restricted(type)) {
if (capable(CAP_SYSLOG))
goto ok;
/*
* For historical reasons, accept CAP_SYS_ADMIN too, with
* a warning.
*/
if (capable(CAP_SYS_ADMIN)) {
pr_warn_once("%s (%d): Attempt to access syslog with "
"CAP_SYS_ADMIN but no CAP_SYSLOG "
"(deprecated).\n",
current->comm, task_pid_nr(current));
goto ok;
}
return -EPERM;
}
ok:
return security_syslog(type);
}
static void append_char(char **pp, char *e, char c)
{
if (*pp < e)
*(*pp)++ = c;
}
static ssize_t msg_print_ext_header(char *buf, size_t size,
struct printk_log *msg, u64 seq,
enum log_flags prev_flags)
{
u64 ts_usec = msg->ts_nsec;
char cont = '-';
do_div(ts_usec, 1000);
/*
* If we couldn't merge continuation line fragments during the print,
* export the stored flags to allow an optional external merge of the
* records. Merging the records isn't always neccessarily correct, like
* when we hit a race during printing. In most cases though, it produces
* better readable output. 'c' in the record flags mark the first
* fragment of a line, '+' the following.
*/
if (msg->flags & LOG_CONT && !(prev_flags & LOG_CONT))
cont = 'c';
else if ((msg->flags & LOG_CONT) ||
((prev_flags & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
cont = '+';
return scnprintf(buf, size, "%u,%llu,%llu,%c;",
(msg->facility << 3) | msg->level, seq, ts_usec, cont);
}
static ssize_t msg_print_ext_body(char *buf, size_t size,
char *dict, size_t dict_len,
char *text, size_t text_len)
{
char *p = buf, *e = buf + size;
size_t i;
/* escape non-printable characters */
for (i = 0; i < text_len; i++) {
unsigned char c = text[i];
if (c < ' ' || c >= 127 || c == '\\')
p += scnprintf(p, e - p, "\\x%02x", c);
else
append_char(&p, e, c);
}
append_char(&p, e, '\n');
if (dict_len) {
bool line = true;
for (i = 0; i < dict_len; i++) {
unsigned char c = dict[i];
if (line) {
append_char(&p, e, ' ');
line = false;
}
if (c == '\0') {
append_char(&p, e, '\n');
line = true;
continue;
}
if (c < ' ' || c >= 127 || c == '\\') {
p += scnprintf(p, e - p, "\\x%02x", c);
continue;
}
append_char(&p, e, c);
}
append_char(&p, e, '\n');
}
return p - buf;
}
/* /dev/kmsg - userspace message inject/listen interface */
struct devkmsg_user {
u64 seq;
u32 idx;
enum log_flags prev;
struct mutex lock;
char buf[CONSOLE_EXT_LOG_MAX];
};
static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
unsigned long count, loff_t pos)
{
char *buf, *line;
int i;
int level = default_message_loglevel;
int facility = 1; /* LOG_USER */
size_t len = iov_length(iv, count);
ssize_t ret = len;
if (len > LOG_LINE_MAX)
return -EINVAL;
buf = kmalloc(len+1, GFP_KERNEL);
if (buf == NULL)
return -ENOMEM;
line = buf;
for (i = 0; i < count; i++) {
if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
ret = -EFAULT;
goto out;
}
line += iv[i].iov_len;
}
/*
* Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
* the decimal value represents 32bit, the lower 3 bit are the log
* level, the rest are the log facility.
*
* If no prefix or no userspace facility is specified, we
* enforce LOG_USER, to be able to reliably distinguish
* kernel-generated messages from userspace-injected ones.
*/
line = buf;
if (line[0] == '<') {
char *endp = NULL;
unsigned int u;
u = simple_strtoul(line + 1, &endp, 10);
if (endp && endp[0] == '>') {
level = LOG_LEVEL(u);
if (LOG_FACILITY(u) != 0)
facility = LOG_FACILITY(u);
endp++;
len -= endp - line;
line = endp;
}
}
line[len] = '\0';
printk_emit(facility, level, NULL, 0, "%s", line);
out:
kfree(buf);
return ret;
}
static ssize_t devkmsg_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
struct devkmsg_user *user = file->private_data;
struct printk_log *msg;
size_t len;
ssize_t ret;
if (!user)
return -EBADF;
ret = mutex_lock_interruptible(&user->lock);
if (ret)
return ret;
raw_spin_lock_irq(&logbuf_lock);
while (user->seq == log_next_seq) {
if (file->f_flags & O_NONBLOCK) {
ret = -EAGAIN;
raw_spin_unlock_irq(&logbuf_lock);
goto out;
}
raw_spin_unlock_irq(&logbuf_lock);
ret = wait_event_interruptible(log_wait,
user->seq != log_next_seq);
if (ret)
goto out;
raw_spin_lock_irq(&logbuf_lock);
}
if (user->seq < log_first_seq) {
/* our last seen message is gone, return error and reset */
user->idx = log_first_idx;
user->seq = log_first_seq;
ret = -EPIPE;
raw_spin_unlock_irq(&logbuf_lock);
goto out;
}
msg = log_from_idx(user->idx);
len = msg_print_ext_header(user->buf, sizeof(user->buf),
msg, user->seq, user->prev);
len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
log_dict(msg), msg->dict_len,
log_text(msg), msg->text_len);
user->prev = msg->flags;
user->idx = log_next(user->idx);
user->seq++;
raw_spin_unlock_irq(&logbuf_lock);
if (len > count) {
ret = -EINVAL;
goto out;
}
if (copy_to_user(buf, user->buf, len)) {
ret = -EFAULT;
goto out;
}
ret = len;
out:
mutex_unlock(&user->lock);
return ret;
}
static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
{
struct devkmsg_user *user = file->private_data;
loff_t ret = 0;
if (!user)
return -EBADF;
if (offset)
return -ESPIPE;
raw_spin_lock_irq(&logbuf_lock);
switch (whence) {
case SEEK_SET:
/* the first record */
user->idx = log_first_idx;
user->seq = log_first_seq;
break;
case SEEK_DATA:
/*
* The first record after the last SYSLOG_ACTION_CLEAR,
* like issued by 'dmesg -c'. Reading /dev/kmsg itself
* changes no global state, and does not clear anything.
*/
user->idx = clear_idx;
user->seq = clear_seq;
break;
case SEEK_END:
/* after the last record */
user->idx = log_next_idx;
user->seq = log_next_seq;
break;
default:
ret = -EINVAL;
}
raw_spin_unlock_irq(&logbuf_lock);
return ret;
}
static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
{
struct devkmsg_user *user = file->private_data;
int ret = 0;
if (!user)
return POLLERR|POLLNVAL;
poll_wait(file, &log_wait, wait);
raw_spin_lock_irq(&logbuf_lock);
if (user->seq < log_next_seq) {
/* return error when data has vanished underneath us */
if (user->seq < log_first_seq)
ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
else
ret = POLLIN|POLLRDNORM;
}
raw_spin_unlock_irq(&logbuf_lock);
return ret;
}
static int devkmsg_open(struct inode *inode, struct file *file)
{
struct devkmsg_user *user;
int err;
/* write-only does not need any file context */
if ((file->f_flags & O_ACCMODE) == O_WRONLY)
return 0;
err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
SYSLOG_FROM_READER);
if (err)
return err;
user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
if (!user)
return -ENOMEM;
mutex_init(&user->lock);
raw_spin_lock_irq(&logbuf_lock);
user->idx = log_first_idx;
user->seq = log_first_seq;
raw_spin_unlock_irq(&logbuf_lock);
file->private_data = user;
return 0;
}
static int devkmsg_release(struct inode *inode, struct file *file)
{
struct devkmsg_user *user = file->private_data;
if (!user)
return 0;
mutex_destroy(&user->lock);
kfree(user);
return 0;
}
const struct file_operations kmsg_fops = {
.open = devkmsg_open,
.read = devkmsg_read,
.aio_write = devkmsg_writev,
.llseek = devkmsg_llseek,
.poll = devkmsg_poll,
.release = devkmsg_release,
};
#ifdef CONFIG_KEXEC
/*
* This appends the listed symbols to /proc/vmcore
*
* /proc/vmcore is used by various utilities, like crash and makedumpfile to
* obtain access to symbols that are otherwise very difficult to locate. These
* symbols are specifically used so that utilities can access and extract the
* dmesg log from a vmcore file after a crash.
*/
void log_buf_kexec_setup(void)
{
VMCOREINFO_SYMBOL(log_buf);
VMCOREINFO_SYMBOL(log_buf_len);
VMCOREINFO_SYMBOL(log_first_idx);
VMCOREINFO_SYMBOL(clear_idx);
VMCOREINFO_SYMBOL(log_next_idx);
/*
* Export struct printk_log size and field offsets. User space tools can
* parse it and detect any changes to structure down the line.
*/
VMCOREINFO_STRUCT_SIZE(printk_log);
VMCOREINFO_OFFSET(printk_log, ts_nsec);
VMCOREINFO_OFFSET(printk_log, len);
VMCOREINFO_OFFSET(printk_log, text_len);
VMCOREINFO_OFFSET(printk_log, dict_len);
}
#endif
/* requested log_buf_len from kernel cmdline */
static unsigned long __initdata new_log_buf_len;
/* we practice scaling the ring buffer by powers of 2 */
static void __init log_buf_len_update(unsigned size)
{
if (size)
size = roundup_pow_of_two(size);
if (size > log_buf_len)
new_log_buf_len = size;
}
/* save requested log_buf_len since it's too early to process it */
static int __init log_buf_len_setup(char *str)
{
unsigned size = memparse(str, &str);
log_buf_len_update(size);
return 0;
}
early_param("log_buf_len", log_buf_len_setup);
#ifdef CONFIG_SMP
#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
static void __init log_buf_add_cpu(void)
{
unsigned int cpu_extra;
/*
* archs should set up cpu_possible_bits properly with
* set_cpu_possible() after setup_arch() but just in
* case lets ensure this is valid.
*/
if (num_possible_cpus() == 1)
return;
cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
/* by default this will only continue through for large > 64 CPUs */
if (cpu_extra <= __LOG_BUF_LEN / 2)
return;
pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
__LOG_CPU_MAX_BUF_LEN);
pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
cpu_extra);
pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
}
#else /* !CONFIG_SMP */
static inline void log_buf_add_cpu(void) {}
#endif /* CONFIG_SMP */
void __init setup_log_buf(int early)
{
unsigned long flags;
char *new_log_buf;
int free;
if (log_buf != __log_buf)
return;
if (!early && !new_log_buf_len)
log_buf_add_cpu();
if (!new_log_buf_len)
return;
if (early) {
new_log_buf =
memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
} else {
new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
LOG_ALIGN);
}
if (unlikely(!new_log_buf)) {
pr_err("log_buf_len: %ld bytes not available\n",
new_log_buf_len);
return;
}
raw_spin_lock_irqsave(&logbuf_lock, flags);
log_buf_len = new_log_buf_len;
log_buf = new_log_buf;
new_log_buf_len = 0;
free = __LOG_BUF_LEN - log_next_idx;
memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
pr_info("log_buf_len: %d bytes\n", log_buf_len);
pr_info("early log buf free: %d(%d%%)\n",
free, (free * 100) / __LOG_BUF_LEN);
}
static bool __read_mostly ignore_loglevel;
static int __init ignore_loglevel_setup(char *str)
{
ignore_loglevel = true;
pr_info("debug: ignoring loglevel setting.\n");
return 0;
}
early_param("ignore_loglevel", ignore_loglevel_setup);
module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(ignore_loglevel,
"ignore loglevel setting (prints all kernel messages to the console)");
static bool should_ignore_loglevel(int level)
{
return (level >= console_loglevel && !ignore_loglevel);
}
#ifdef CONFIG_BOOT_PRINTK_DELAY
static int boot_delay; /* msecs delay after each printk during bootup */
static unsigned long long loops_per_msec; /* based on boot_delay */
static int __init boot_delay_setup(char *str)
{
unsigned long lpj;
lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
get_option(&str, &boot_delay);
if (boot_delay > 10 * 1000)
boot_delay = 0;
pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
"HZ: %d, loops_per_msec: %llu\n",
boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
return 0;
}
early_param("boot_delay", boot_delay_setup);
static void boot_delay_msec(int level)
{
unsigned long long k;
unsigned long timeout;
if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
|| should_ignore_loglevel(level)) {
return;
}
k = (unsigned long long)loops_per_msec * boot_delay;
timeout = jiffies + msecs_to_jiffies(boot_delay);
while (k) {
k--;
cpu_relax();
/*
* use (volatile) jiffies to prevent
* compiler reduction; loop termination via jiffies
* is secondary and may or may not happen.
*/
if (time_after(jiffies, timeout))
break;
touch_nmi_watchdog();
}
}
#else
static inline void boot_delay_msec(int level)
{
}
#endif
static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
static size_t print_time(u64 ts, char *buf)
{
unsigned long rem_nsec;
if (!printk_time)
return 0;
rem_nsec = do_div(ts, 1000000000);
if (!buf)
return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
return sprintf(buf, "[%5lu.%06lu] ",
(unsigned long)ts, rem_nsec / 1000);
}
static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
{
size_t len = 0;
unsigned int prefix = (msg->facility << 3) | msg->level;
if (syslog) {
if (buf) {
len += sprintf(buf, "<%u>", prefix);
} else {
len += 3;
if (prefix > 999)
len += 3;
else if (prefix > 99)
len += 2;
else if (prefix > 9)
len++;
}
}
len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
return len;
}
static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
bool syslog, char *buf, size_t size)
{
const char *text = log_text(msg);
size_t text_size = msg->text_len;
bool prefix = true;
bool newline = true;
size_t len = 0;
if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
prefix = false;
if (msg->flags & LOG_CONT) {
if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
prefix = false;
if (!(msg->flags & LOG_NEWLINE))
newline = false;
}
do {
const char *next = memchr(text, '\n', text_size);
size_t text_len;
if (next) {
text_len = next - text;
next++;
text_size -= next - text;
} else {
text_len = text_size;
}
if (buf) {
if (print_prefix(msg, syslog, NULL) +
text_len + 1 >= size - len)
break;
if (prefix)
len += print_prefix(msg, syslog, buf + len);
memcpy(buf + len, text, text_len);
len += text_len;
if (next || newline)
buf[len++] = '\n';
} else {
/* SYSLOG_ACTION_* buffer size only calculation */
if (prefix)
len += print_prefix(msg, syslog, NULL);
len += text_len;
if (next || newline)
len++;
}
prefix = true;
text = next;
} while (text);
return len;
}
static int syslog_print(char __user *buf, int size)
{
char *text;
struct printk_log *msg;
int len = 0;
text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
if (!text)
return -ENOMEM;
while (size > 0) {
size_t n;
size_t skip;
raw_spin_lock_irq(&logbuf_lock);
if (syslog_seq < log_first_seq) {
/* messages are gone, move to first one */
syslog_seq = log_first_seq;
syslog_idx = log_first_idx;
syslog_prev = 0;
syslog_partial = 0;
}
if (syslog_seq == log_next_seq) {
raw_spin_unlock_irq(&logbuf_lock);
break;
}
skip = syslog_partial;
msg = log_from_idx(syslog_idx);
n = msg_print_text(msg, syslog_prev, true, text,
LOG_LINE_MAX + PREFIX_MAX);
if (n - syslog_partial <= size) {
/* message fits into buffer, move forward */
syslog_idx = log_next(syslog_idx);
syslog_seq++;
syslog_prev = msg->flags;
n -= syslog_partial;
syslog_partial = 0;
} else if (!len){
/* partial read(), remember position */
n = size;
syslog_partial += n;
} else
n = 0;
raw_spin_unlock_irq(&logbuf_lock);
if (!n)
break;
if (copy_to_user(buf, text + skip, n)) {
if (!len)
len = -EFAULT;
break;
}
len += n;
size -= n;
buf += n;
}
kfree(text);
return len;
}
static int syslog_print_all(char __user *buf, int size, bool clear)
{
char *text;
int len = 0;
text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
if (!text)
return -ENOMEM;
raw_spin_lock_irq(&logbuf_lock);
if (buf) {
u64 next_seq;
u64 seq;
u32 idx;
enum log_flags prev;
/*
* Find first record that fits, including all following records,
* into the user-provided buffer for this dump.
*/
seq = clear_seq;
idx = clear_idx;
prev = 0;
while (seq < log_next_seq) {
struct printk_log *msg = log_from_idx(idx);
len += msg_print_text(msg, prev, true, NULL, 0);
prev = msg->flags;
idx = log_next(idx);
seq++;
}
/* move first record forward until length fits into the buffer */
seq = clear_seq;
idx = clear_idx;
prev = 0;
while (len > size && seq < log_next_seq) {
struct printk_log *msg = log_from_idx(idx);
len -= msg_print_text(msg, prev, true, NULL, 0);
prev = msg->flags;
idx = log_next(idx);
seq++;
}
/* last message fitting into this dump */
next_seq = log_next_seq;
len = 0;
while (len >= 0 && seq < next_seq) {
struct printk_log *msg = log_from_idx(idx);
int textlen;
textlen = msg_print_text(msg, prev, true, text,
LOG_LINE_MAX + PREFIX_MAX);
if (textlen < 0) {
len = textlen;
break;
}
idx = log_next(idx);
seq++;
prev = msg->flags;
raw_spin_unlock_irq(&logbuf_lock);
if (copy_to_user(buf + len, text, textlen))
len = -EFAULT;
else
len += textlen;
raw_spin_lock_irq(&logbuf_lock);
if (seq < log_first_seq) {
/* messages are gone, move to next one */
seq = log_first_seq;
idx = log_first_idx;
prev = 0;
}
}
}
if (clear) {
clear_seq = log_next_seq;
clear_idx = log_next_idx;
}
raw_spin_unlock_irq(&logbuf_lock);
kfree(text);
return len;
}
int do_syslog(int type, char __user *buf, int len, int source)
{
bool clear = false;
static int saved_console_loglevel = LOGLEVEL_DEFAULT;
int error;
error = check_syslog_permissions(type, source);
if (error)
goto out;
switch (type) {
case SYSLOG_ACTION_CLOSE: /* Close log */
break;
case SYSLOG_ACTION_OPEN: /* Open log */
break;
case SYSLOG_ACTION_READ: /* Read from log */
error = -EINVAL;
if (!buf || len < 0)
goto out;
error = 0;
if (!len)
goto out;
if (!access_ok(VERIFY_WRITE, buf, len)) {
error = -EFAULT;
goto out;
}
error = wait_event_interruptible(log_wait,
syslog_seq != log_next_seq);
if (error)
goto out;
error = syslog_print(buf, len);
break;
/* Read/clear last kernel messages */
case SYSLOG_ACTION_READ_CLEAR:
clear = true;
/* FALL THRU */
/* Read last kernel messages */
case SYSLOG_ACTION_READ_ALL:
error = -EINVAL;
if (!buf || len < 0)
goto out;
error = 0;
if (!len)
goto out;
if (!access_ok(VERIFY_WRITE, buf, len)) {
error = -EFAULT;
goto out;
}
error = syslog_print_all(buf, len, clear);
break;
/* Clear ring buffer */
case SYSLOG_ACTION_CLEAR:
syslog_print_all(NULL, 0, true);
break;
/* Disable logging to console */
case SYSLOG_ACTION_CONSOLE_OFF:
if (saved_console_loglevel == LOGLEVEL_DEFAULT)
saved_console_loglevel = console_loglevel;
console_loglevel = minimum_console_loglevel;
break;
/* Enable logging to console */
case SYSLOG_ACTION_CONSOLE_ON:
if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
console_loglevel = saved_console_loglevel;
saved_console_loglevel = LOGLEVEL_DEFAULT;
}
break;
/* Set level of messages printed to console */
case SYSLOG_ACTION_CONSOLE_LEVEL:
error = -EINVAL;
if (len < 1 || len > 8)
goto out;
if (len < minimum_console_loglevel)
len = minimum_console_loglevel;
console_loglevel = len;
/* Implicitly re-enable logging to console */
saved_console_loglevel = LOGLEVEL_DEFAULT;
error = 0;
break;
/* Number of chars in the log buffer */
case SYSLOG_ACTION_SIZE_UNREAD:
raw_spin_lock_irq(&logbuf_lock);
if (syslog_seq < log_first_seq) {
/* messages are gone, move to first one */
syslog_seq = log_first_seq;
syslog_idx = log_first_idx;
syslog_prev = 0;
syslog_partial = 0;
}
if (source == SYSLOG_FROM_PROC) {
/*
* Short-cut for poll(/"proc/kmsg") which simply checks
* for pending data, not the size; return the count of
* records, not the length.
*/
error = log_next_seq - syslog_seq;
} else {
u64 seq = syslog_seq;
u32 idx = syslog_idx;
enum log_flags prev = syslog_prev;
error = 0;
while (seq < log_next_seq) {
struct printk_log *msg = log_from_idx(idx);
error += msg_print_text(msg, prev, true, NULL, 0);
idx = log_next(idx);
seq++;
prev = msg->flags;
}
error -= syslog_partial;
}
raw_spin_unlock_irq(&logbuf_lock);
break;
/* Size of the log buffer */
case SYSLOG_ACTION_SIZE_BUFFER:
error = log_buf_len;
break;
default:
error = -EINVAL;
break;
}
out:
return error;
}
SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
{
return do_syslog(type, buf, len, SYSLOG_FROM_READER);
}
/*
* Call the console drivers, asking them to write out
* log_buf[start] to log_buf[end - 1].
* The console_lock must be held.
*/
static void call_console_drivers(int level,
const char *ext_text, size_t ext_len,
const char *text, size_t len)
{
struct console *con;
trace_console(text, len);
if (!console_drivers)
return;
for_each_console(con) {
if (exclusive_console && con != exclusive_console)
continue;
if (!(con->flags & CON_ENABLED))
continue;
if (!con->write)
continue;
if (!cpu_online(smp_processor_id()) &&
!(con->flags & CON_ANYTIME))
continue;
if (con->flags & CON_EXTENDED)
con->write(con, ext_text, ext_len);
else
con->write(con, text, len);
}
}
/*
* Zap console related locks when oopsing.
* To leave time for slow consoles to print a full oops,
* only zap at most once every 30 seconds.
*/
static void zap_locks(void)
{
static unsigned long oops_timestamp;
if (time_after_eq(jiffies, oops_timestamp) &&
!time_after(jiffies, oops_timestamp + 30 * HZ))
return;
oops_timestamp = jiffies;
debug_locks_off();
/* If a crash is occurring, make sure we can't deadlock */
raw_spin_lock_init(&logbuf_lock);
/* And make sure that we print immediately */
sema_init(&console_sem, 1);
}
int printk_delay_msec __read_mostly;
static inline void printk_delay(void)
{
if (unlikely(printk_delay_msec)) {
int m = printk_delay_msec;
while (m--) {
mdelay(1);
touch_nmi_watchdog();
}
}
}
/*
* Continuation lines are buffered, and not committed to the record buffer
* until the line is complete, or a race forces it. The line fragments
* though, are printed immediately to the consoles to ensure everything has
* reached the console in case of a kernel crash.
*/
static struct cont {
char buf[LOG_LINE_MAX];
size_t len; /* length == 0 means unused buffer */
size_t cons; /* bytes written to console */
struct task_struct *owner; /* task of first print*/
u64 ts_nsec; /* time of first print */
u8 level; /* log level of first message */
u8 facility; /* log facility of first message */
enum log_flags flags; /* prefix, newline flags */
bool flushed:1; /* buffer sealed and committed */
} cont;
static void cont_flush(enum log_flags flags)
{
if (cont.flushed)
return;
if (cont.len == 0)
return;
if (cont.cons) {
/*
* If a fragment of this line was directly flushed to the
* console; wait for the console to pick up the rest of the
* line. LOG_NOCONS suppresses a duplicated output.
*/
log_store(cont.facility, cont.level, flags | LOG_NOCONS,
cont.ts_nsec, NULL, 0, cont.buf, cont.len);
cont.flags = flags;
cont.flushed = true;
} else {
/*
* If no fragment of this line ever reached the console,
* just submit it to the store and free the buffer.
*/
log_store(cont.facility, cont.level, flags, 0,
NULL, 0, cont.buf, cont.len);
cont.len = 0;
}
}
static bool cont_add(int facility, int level, const char *text, size_t len)
{
if (cont.len && cont.flushed)
return false;
/*
* If ext consoles are present, flush and skip in-kernel
* continuation. See nr_ext_console_drivers definition. Also, if
* the line gets too long, split it up in separate records.
*/
if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
cont_flush(LOG_CONT);
return false;
}
if (!cont.len) {
cont.facility = facility;
cont.level = level;
cont.owner = current;
cont.ts_nsec = local_clock();
cont.flags = 0;
cont.cons = 0;
cont.flushed = false;
}
memcpy(cont.buf + cont.len, text, len);
cont.len += len;
if (cont.len > (sizeof(cont.buf) * 80) / 100)
cont_flush(LOG_CONT);
return true;
}
static size_t cont_print_text(char *text, size_t size)
{
size_t textlen = 0;
size_t len;
if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
textlen += print_time(cont.ts_nsec, text);
size -= textlen;
}
len = cont.len - cont.cons;
if (len > 0) {
if (len+1 > size)
len = size-1;
memcpy(text + textlen, cont.buf + cont.cons, len);
textlen += len;
cont.cons = cont.len;
}
if (cont.flushed) {
if (cont.flags & LOG_NEWLINE)
text[textlen++] = '\n';
/* got everything, release buffer */
cont.len = 0;
}
return textlen;
}
asmlinkage int vprintk_emit(int facility, int level,
const char *dict, size_t dictlen,
const char *fmt, va_list args)
{
/* cpu currently holding logbuf_lock in this function */
static unsigned int logbuf_cpu = UINT_MAX;
static bool recursion_bug;
static char textbuf[LOG_LINE_MAX];
char *text = textbuf;
size_t text_len = 0;
enum log_flags lflags = 0;
unsigned long flags;
int this_cpu;
int printed_len = 0;
int nmi_message_lost;
bool in_sched = false;
/* do not print the KERN_CONT buffer asynchronously */
bool has_cont_msg = false;
if (level == LOGLEVEL_SCHED) {
level = LOGLEVEL_DEFAULT;
in_sched = true;
}
boot_delay_msec(level);
printk_delay();
local_irq_save(flags);
this_cpu = smp_processor_id();
/*
* Ouch, printk recursed into itself!
*/
if (unlikely(logbuf_cpu == this_cpu)) {
/*
* If a crash is occurring during printk() on this CPU,
* then try to get the crash message out but make sure
* we can't deadlock. Otherwise just return to avoid the
* recursion and return - but flag the recursion so that
* it can be printed at the next appropriate moment:
*/
if (!oops_in_progress && !lockdep_recursing(current)) {
recursion_bug = true;
local_irq_restore(flags);
return 0;
}
zap_locks();
}
lockdep_off();
/* This stops the holder of console_sem just where we want him */
raw_spin_lock(&logbuf_lock);
logbuf_cpu = this_cpu;
if (unlikely(recursion_bug)) {
static const char recursion_msg[] =
"BUG: recent printk recursion!";
recursion_bug = false;
/* emit KERN_CRIT message */
printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
NULL, 0, recursion_msg,
strlen(recursion_msg));
}
nmi_message_lost = get_nmi_message_lost();
if (unlikely(nmi_message_lost)) {
text_len = scnprintf(textbuf, sizeof(textbuf),
"BAD LUCK: lost %d message(s) from NMI context!",
nmi_message_lost);
printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
NULL, 0, textbuf, text_len);
}
/*
* The printf needs to come first; we need the syslog
* prefix which might be passed-in as a parameter.
*/
text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
/* mark and strip a trailing newline */
if (text_len && text[text_len-1] == '\n') {
text_len--;
lflags |= LOG_NEWLINE;
}
/* strip kernel syslog prefix and extract log level or control flags */
if (facility == 0) {
int kern_level = printk_get_level(text);
if (kern_level) {
const char *end_of_header = printk_skip_level(text);
switch (kern_level) {
case '0' ... '7':
if (level == LOGLEVEL_DEFAULT)
level = kern_level - '0';
/* fallthrough */
case 'd': /* KERN_DEFAULT */
lflags |= LOG_PREFIX;
}
/*
* No need to check length here because vscnprintf
* put '\0' at the end of the string. Only valid and
* newly printed level is detected.
*/
text_len -= end_of_header - text;
text = (char *)end_of_header;
}
}
#ifdef CONFIG_EARLY_PRINTK_DIRECT
printascii(text);
#endif
if (level == LOGLEVEL_DEFAULT)
level = default_message_loglevel;
if (dict)
lflags |= LOG_PREFIX|LOG_NEWLINE;
if (!(lflags & LOG_NEWLINE)) {
has_cont_msg = true;
/*
* Flush the conflicting buffer. An earlier newline was missing,
* or another task also prints continuation lines.
*/
if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
cont_flush(LOG_NEWLINE);
/* buffer line if possible, otherwise store it right away */
if (cont_add(facility, level, text, text_len))
printed_len += text_len;
else
printed_len += log_store(facility, level,
lflags | LOG_CONT, 0,
dict, dictlen, text, text_len);
} else {
bool stored = false;
/*
* If an earlier newline was missing and it was the same task,
* either merge it with the current buffer and flush, or if
* there was a race with interrupts (prefix == true) then just
* flush it out and store this line separately.
* If the preceding printk was from a different task and missed
* a newline, flush and append the newline.
*/
if (cont.len) {
if (cont.owner == current && !(lflags & LOG_PREFIX))
stored = cont_add(facility, level, text,
text_len);
cont_flush(LOG_NEWLINE);
has_cont_msg = true;
}
if (stored)
printed_len += text_len;
else
printed_len += log_store(facility, level, lflags, 0,
dict, dictlen, text, text_len);
}
logbuf_cpu = UINT_MAX;
raw_spin_unlock(&logbuf_lock);
lockdep_on();
local_irq_restore(flags);
/* If called from the scheduler, we can not call up(). */
if (!in_sched) {
lockdep_off();
/*
* Attempt to print the messages to console asynchronously so
* that the kernel doesn't get stalled due to slow serial
* console. That can lead to softlockups, lost interrupts, or
* userspace timing out under heavy printing load.
*
* However we resort to synchronous printing of messages during
* early boot, when synchronous printing was explicitly
* requested by a kernel parameter, when we have a KERN_CONT
* buffer to print, or when console_verbose() was called to
* print everything during panic / oops.
* Unlike bust_spinlocks() and oops_in_progress,
* console_verbose() sets console_loglevel to MOTORMOUTH and
* never clears it, while oops_in_progress can go back to 0,
* switching printk back to async mode; we want printk to
* operate in sync mode once panic() occurred.
*/
if (console_loglevel != CONSOLE_LOGLEVEL_MOTORMOUTH &&
can_printk_async() &&
!has_cont_msg) {
/* Offload printing to a schedulable context. */
printk_kthread_need_flush_console = true;
wake_up_process(printk_kthread);
} else {
/*
* Try to acquire and then immediately release the
* console semaphore. The release will print out
* buffers and wake up /dev/kmsg and syslog() users.
*/
if (console_trylock())
console_unlock();
}
lockdep_on();
}
return printed_len;
}
EXPORT_SYMBOL(vprintk_emit);
asmlinkage int vprintk(const char *fmt, va_list args)
{
return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
}
EXPORT_SYMBOL(vprintk);
asmlinkage int printk_emit(int facility, int level,
const char *dict, size_t dictlen,
const char *fmt, ...)
{
va_list args;
int r;
va_start(args, fmt);
r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
va_end(args);
return r;
}
EXPORT_SYMBOL(printk_emit);
int vprintk_default(const char *fmt, va_list args)
{
int r;
#ifdef CONFIG_KGDB_KDB
if (unlikely(kdb_trap_printk)) {
r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
return r;
}
#endif
r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
return r;
}
EXPORT_SYMBOL_GPL(vprintk_default);
/**
* printk - print a kernel message
* @fmt: format string
*
* This is printk(). It can be called from any context. We want it to work.
*
* We try to grab the console_lock. If we succeed, it's easy - we log the
* output and call the console drivers. If we fail to get the semaphore, we
* place the output into the log buffer and return. The current holder of
* the console_sem will notice the new output in console_unlock(); and will
* send it to the consoles before releasing the lock.
*
* One effect of this deferred printing is that code which calls printk() and
* then changes console_loglevel may break. This is because console_loglevel
* is inspected when the actual printing occurs.
*
* See also:
* printf(3)
*
* See the vsnprintf() documentation for format string extensions over C99.
*/
asmlinkage int printk(const char *fmt, ...)
{
va_list args;
int r;
va_start(args, fmt);
r = vprintk_func(fmt, args);
va_end(args);
return r;
}
EXPORT_SYMBOL(printk);
#else /* CONFIG_PRINTK */
#define LOG_LINE_MAX 0
#define PREFIX_MAX 0
static u64 syslog_seq;
static u32 syslog_idx;
static u64 console_seq;
static u32 console_idx;
static enum log_flags syslog_prev;
static u64 log_first_seq;
static u32 log_first_idx;
static u64 log_next_seq;
static enum log_flags console_prev;
static struct cont {
size_t len;
size_t cons;
u8 level;
bool flushed:1;
} cont;
static char *log_text(const struct printk_log *msg) { return NULL; }
static char *log_dict(const struct printk_log *msg) { return NULL; }
static struct printk_log *log_from_idx(u32 idx) { return NULL; }
static u32 log_next(u32 idx) { return 0; }
static ssize_t msg_print_ext_header(char *buf, size_t size,
struct printk_log *msg, u64 seq,
enum log_flags prev_flags) { return 0; }
static ssize_t msg_print_ext_body(char *buf, size_t size,
char *dict, size_t dict_len,
char *text, size_t text_len) { return 0; }
static void call_console_drivers(int level,
const char *ext_text, size_t ext_len,
const char *text, size_t len) {}
static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
bool syslog, char *buf, size_t size) { return 0; }
static size_t cont_print_text(char *text, size_t size) { return 0; }
static bool should_ignore_loglevel(int level) { return false; }
/* Still needs to be defined for users */
DEFINE_PER_CPU(printk_func_t, printk_func);
#endif /* CONFIG_PRINTK */
#ifdef CONFIG_EARLY_PRINTK
struct console *early_console;
asmlinkage void early_printk(const char *fmt, ...)
{
va_list ap;
char buf[512];
int n;
if (!early_console)
return;
va_start(ap, fmt);
n = vscnprintf(buf, sizeof(buf), fmt, ap);
va_end(ap);
early_console->write(early_console, buf, n);
}
#endif
static int __add_preferred_console(char *name, int idx, char *options,
char *brl_options)
{
struct console_cmdline *c;
int i;
/*
* See if this tty is not yet registered, and
* if we have a slot free.
*/
for (i = 0, c = console_cmdline;
i < MAX_CMDLINECONSOLES && c->name[0];
i++, c++) {
if (strcmp(c->name, name) == 0 && c->index == idx) {
if (!brl_options)
selected_console = i;
return 0;
}
}
if (i == MAX_CMDLINECONSOLES)
return -E2BIG;
if (!brl_options)
selected_console = i;
strlcpy(c->name, name, sizeof(c->name));
c->options = options;
braille_set_options(c, brl_options);
c->index = idx;
return 0;
}
/*
* Set up a console. Called via do_early_param() in init/main.c
* for each "console=" parameter in the boot command line.
*/
static int __init console_setup(char *str)
{
char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
char *s, *options, *brl_options = NULL;
int idx;
if (_braille_console_setup(&str, &brl_options))
return 1;
/*
* Decode str into name, index, options.
*/
if (str[0] >= '0' && str[0] <= '9') {
strcpy(buf, "ttyS");
strncpy(buf + 4, str, sizeof(buf) - 5);
} else {
strncpy(buf, str, sizeof(buf) - 1);
}
buf[sizeof(buf) - 1] = 0;
options = strchr(str, ',');
if (options)
*(options++) = 0;
#ifdef __sparc__
if (!strcmp(str, "ttya"))
strcpy(buf, "ttyS0");
if (!strcmp(str, "ttyb"))
strcpy(buf, "ttyS1");
#endif
for (s = buf; *s; s++)
if (isdigit(*s) || *s == ',')
break;
idx = simple_strtoul(s, NULL, 10);
*s = 0;
__add_preferred_console(buf, idx, options, brl_options);
console_set_on_cmdline = 1;
return 1;
}
__setup("console=", console_setup);
/**
* add_preferred_console - add a device to the list of preferred consoles.
* @name: device name
* @idx: device index
* @options: options for this console
*
* The last preferred console added will be used for kernel messages
* and stdin/out/err for init. Normally this is used by console_setup
* above to handle user-supplied console arguments; however it can also
* be used by arch-specific code either to override the user or more
* commonly to provide a default console (ie from PROM variables) when
* the user has not supplied one.
*/
int add_preferred_console(char *name, int idx, char *options)
{
return __add_preferred_console(name, idx, options, NULL);
}
int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
{
struct console_cmdline *c;
int i;
for (i = 0, c = console_cmdline;
i < MAX_CMDLINECONSOLES && c->name[0];
i++, c++)
if (strcmp(c->name, name) == 0 && c->index == idx) {
strlcpy(c->name, name_new, sizeof(c->name));
c->options = options;
c->index = idx_new;
return i;
}
/* not found */
return -1;
}
bool console_suspend_enabled = true;
EXPORT_SYMBOL(console_suspend_enabled);
static int __init console_suspend_disable(char *str)
{
console_suspend_enabled = false;
return 1;
}
__setup("no_console_suspend", console_suspend_disable);
module_param_named(console_suspend, console_suspend_enabled,
bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
" and hibernate operations");
/* check current suspend/resume status of the console */
int is_console_suspended(void)
{
return console_suspended;
}
/**
* suspend_console - suspend the console subsystem
*
* This disables printk() while we go into suspend states
*/
void suspend_console(void)
{
if (!console_suspend_enabled)
return;
printk("Suspending console(s) (use no_console_suspend to debug)\n");
console_lock();
console_suspended = 1;
up_console_sem();
}
void resume_console(void)
{
if (!console_suspend_enabled)
return;
down_console_sem();
console_suspended = 0;
console_unlock();
}
static void __cpuinit console_flush(struct work_struct *work)
{
console_lock();
console_unlock();
}
static __cpuinitdata DECLARE_WORK(console_cpu_notify_work, console_flush);
/**
* console_cpu_notify - print deferred console messages after CPU hotplug
* @self: notifier struct
* @action: CPU hotplug event
* @hcpu: unused
*
* If printk() is called from a CPU that is not online yet, the messages
* will be spooled but will not show up on the console. This function is
* called when a new CPU comes online (or fails to come up), and ensures
* that any such output gets printed.
*
* Special handling must be done for cases invoked from an atomic context,
* as we can't be taking the console semaphore here.
*/
static int __cpuinit console_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
switch (action) {
case CPU_DEAD:
case CPU_DOWN_FAILED:
case CPU_UP_CANCELED:
#ifdef CONFIG_CONSOLE_FLUSH_ON_HOTPLUG
console_lock();
console_unlock();
#endif
break;
case CPU_ONLINE:
case CPU_DYING:
/* invoked with preemption disabled, so defer */
if (!console_trylock())
schedule_work(&console_cpu_notify_work);
else
console_unlock();
}
return NOTIFY_OK;
}
/**
* console_lock - lock the console system for exclusive use.
*
* Acquires a lock which guarantees that the caller has
* exclusive access to the console system and the console_drivers list.
*
* Can sleep, returns nothing.
*/
void console_lock(void)
{
might_sleep();
down_console_sem();
if (console_suspended)
return;
console_locked = 1;
console_may_schedule = 1;
}
EXPORT_SYMBOL(console_lock);
/**
* console_trylock - try to lock the console system for exclusive use.
*
* Try to acquire a lock which guarantees that the caller has exclusive
* access to the console system and the console_drivers list.
*
* returns 1 on success, and 0 on failure to acquire the lock.
*/
int console_trylock(void)
{
if (down_trylock_console_sem())
return 0;
if (console_suspended) {
up_console_sem();
return 0;
}
console_locked = 1;
/*
* When PREEMPT_COUNT disabled we can't reliably detect if it's
* safe to schedule (e.g. calling printk while holding a spin_lock),
* because preempt_disable()/preempt_enable() are just barriers there
* and preempt_count() is always 0.
*
* RCU read sections have a separate preemption counter when
* PREEMPT_RCU enabled thus we must take extra care and check
* rcu_preempt_depth(), otherwise RCU read sections modify
* preempt_count().
*/
console_may_schedule = !oops_in_progress &&
preemptible() &&
!rcu_preempt_depth();
return 1;
}
EXPORT_SYMBOL(console_trylock);
int is_console_locked(void)
{
return console_locked;
}
/*
* Check if we have any console that is capable of printing while cpu is
* booting or shutting down. Requires console_sem.
*/
static int have_callable_console(void)
{
struct console *con;
for_each_console(con)
if ((con->flags & CON_ENABLED) &&
(con->flags & CON_ANYTIME))
return 1;
return 0;
}
/*
* Can we actually use the console at this time on this cpu?
*
* Console drivers may assume that per-cpu resources have been allocated. So
* unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
* call them until this CPU is officially up.
*/
static inline int can_use_console(void)
{
return cpu_online(raw_smp_processor_id()) || have_callable_console();
}
static void console_cont_flush(char *text, size_t size)
{
unsigned long flags;
size_t len;
raw_spin_lock_irqsave(&logbuf_lock, flags);
if (!cont.len)
goto out;
if (should_ignore_loglevel(cont.level)) {
cont.cons = cont.len;
if (cont.flushed)
cont.len = 0;
goto out;
}
/*
* We still queue earlier records, likely because the console was
* busy. The earlier ones need to be printed before this one, we
* did not flush any fragment so far, so just let it queue up.
*/
if (console_seq < log_next_seq && !cont.cons)
goto out;
len = cont_print_text(text, size);
raw_spin_unlock(&logbuf_lock);
stop_critical_timings();
call_console_drivers(cont.level, NULL, 0, text, len);
start_critical_timings();
local_irq_restore(flags);
return;
out:
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
}
/**
* console_unlock - unlock the console system
*
* Releases the console_lock which the caller holds on the console system
* and the console driver list.
*
* While the console_lock was held, console output may have been buffered
* by printk(). If this is the case, console_unlock(); emits
* the output prior to releasing the lock.
*
* If there is output waiting, we wake /dev/kmsg and syslog() users.
*
* console_unlock(); may be called from any context.
*/
void console_unlock(void)
{
static char ext_text[CONSOLE_EXT_LOG_MAX];
static char text[LOG_LINE_MAX + PREFIX_MAX];
static u64 seen_seq;
unsigned long flags;
bool wake_klogd = false;
bool do_cond_resched, retry;
if (console_suspended) {
up_console_sem();
return;
}
/*
* Console drivers are called under logbuf_lock, so
* @console_may_schedule should be cleared before; however, we may
* end up dumping a lot of lines, for example, if called from
* console registration path, and should invoke cond_resched()
* between lines if allowable. Not doing so can cause a very long
* scheduling stall on a slow console leading to RCU stall and
* softlockup warnings which exacerbate the issue with more
* messages practically incapacitating the system.
*/
do_cond_resched = console_may_schedule;
console_may_schedule = 0;
again:
/*
* We released the console_sem lock, so we need to recheck if
* cpu is online and (if not) is there at least one CON_ANYTIME
* console.
*/
if (!can_use_console()) {
console_locked = 0;
up_console_sem();
return;
}
/* flush buffered message fragment immediately to console */
console_cont_flush(text, sizeof(text));
for (;;) {
struct printk_log *msg;
size_t ext_len = 0;
size_t len;
int level;
raw_spin_lock_irqsave(&logbuf_lock, flags);
if (seen_seq != log_next_seq) {
wake_klogd = true;
seen_seq = log_next_seq;
}
if (console_seq < log_first_seq) {
len = sprintf(text, "** %u printk messages dropped ** ",
(unsigned)(log_first_seq - console_seq));
/* messages are gone, move to first one */
console_seq = log_first_seq;
console_idx = log_first_idx;
console_prev = 0;
} else {
len = 0;
}
skip:
if (console_seq == log_next_seq)
break;
msg = log_from_idx(console_idx);
level = msg->level;
if ((msg->flags & LOG_NOCONS) ||
should_ignore_loglevel(level)) {
/*
* Skip record we have buffered and already printed
* directly to the console when we received it, and
* record that has level above the console loglevel.
*/
console_idx = log_next(console_idx);
console_seq++;
/*
* We will get here again when we register a new
* CON_PRINTBUFFER console. Clear the flag so we
* will properly dump everything later.
*/
msg->flags &= ~LOG_NOCONS;
console_prev = msg->flags;
goto skip;
}
len += msg_print_text(msg, console_prev, false,
text + len, sizeof(text) - len);
if (nr_ext_console_drivers) {
ext_len = msg_print_ext_header(ext_text,
sizeof(ext_text),
msg, console_seq, console_prev);
ext_len += msg_print_ext_body(ext_text + ext_len,
sizeof(ext_text) - ext_len,
log_dict(msg), msg->dict_len,
log_text(msg), msg->text_len);
}
console_idx = log_next(console_idx);
console_seq++;
console_prev = msg->flags;
raw_spin_unlock(&logbuf_lock);
stop_critical_timings(); /* don't trace print latency */
call_console_drivers(level, ext_text, ext_len, text, len);
start_critical_timings();
local_irq_restore(flags);
if (do_cond_resched)
cond_resched();
}
console_locked = 0;
/* Release the exclusive_console once it is used */
if (unlikely(exclusive_console))
exclusive_console = NULL;
raw_spin_unlock(&logbuf_lock);
up_console_sem();
/*
* Someone could have filled up the buffer again, so re-check if there's
* something to flush. In case we cannot trylock the console_sem again,
* there's a new owner and the console_unlock() from them will do the
* flush, no worries.
*/
raw_spin_lock(&logbuf_lock);
retry = console_seq != log_next_seq;
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
if (retry && console_trylock())
goto again;
if (wake_klogd)
wake_up_klogd();
}
EXPORT_SYMBOL(console_unlock);
/**
* console_conditional_schedule - yield the CPU if required
*
* If the console code is currently allowed to sleep, and
* if this CPU should yield the CPU to another task, do
* so here.
*
* Must be called within console_lock();.
*/
void __sched console_conditional_schedule(void)
{
if (console_may_schedule)
cond_resched();
}
EXPORT_SYMBOL(console_conditional_schedule);
void console_unblank(void)
{
struct console *c;
/*
* console_unblank can no longer be called in interrupt context unless
* oops_in_progress is set to 1..
*/
if (oops_in_progress) {
if (down_trylock_console_sem() != 0)
return;
} else
console_lock();
console_locked = 1;
console_may_schedule = 0;
for_each_console(c)
if ((c->flags & CON_ENABLED) && c->unblank)
c->unblank();
console_unlock();
}
/**
* console_flush_on_panic - flush console content on panic
*
* Immediately output all pending messages no matter what.
*/
void console_flush_on_panic(void)
{
/*
* If someone else is holding the console lock, trylock will fail
* and may_schedule may be set. Ignore and proceed to unlock so
* that messages are flushed out. As this can be called from any
* context and we don't want to get preempted while flushing,
* ensure may_schedule is cleared.
*/
console_trylock();
console_may_schedule = 0;
console_unlock();
}
/*
* Return the console tty driver structure and its associated index
*/
struct tty_driver *console_device(int *index)
{
struct console *c;
struct tty_driver *driver = NULL;
console_lock();
for_each_console(c) {
if (!c->device)
continue;
driver = c->device(c, index);
if (driver)
break;
}
console_unlock();
return driver;
}
/*
* Prevent further output on the passed console device so that (for example)
* serial drivers can disable console output before suspending a port, and can
* re-enable output afterwards.
*/
void console_stop(struct console *console)
{
console_lock();
console->flags &= ~CON_ENABLED;
console_unlock();
}
EXPORT_SYMBOL(console_stop);
void console_start(struct console *console)
{
console_lock();
console->flags |= CON_ENABLED;
console_unlock();
}
EXPORT_SYMBOL(console_start);
static int __read_mostly keep_bootcon;
static int __init keep_bootcon_setup(char *str)
{
keep_bootcon = 1;
pr_info("debug: skip boot console de-registration.\n");
return 0;
}
early_param("keep_bootcon", keep_bootcon_setup);
/*
* The console driver calls this routine during kernel initialization
* to register the console printing procedure with printk() and to
* print any messages that were printed by the kernel before the
* console driver was initialized.
*
* This can happen pretty early during the boot process (because of
* early_printk) - sometimes before setup_arch() completes - be careful
* of what kernel features are used - they may not be initialised yet.
*
* There are two types of consoles - bootconsoles (early_printk) and
* "real" consoles (everything which is not a bootconsole) which are
* handled differently.
* - Any number of bootconsoles can be registered at any time.
* - As soon as a "real" console is registered, all bootconsoles
* will be unregistered automatically.
* - Once a "real" console is registered, any attempt to register a
* bootconsoles will be rejected
*/
void register_console(struct console *newcon)
{
int i;
unsigned long flags;
struct console *bcon = NULL;
struct console_cmdline *c;
if (console_drivers)
for_each_console(bcon)
if (WARN(bcon == newcon,
"console '%s%d' already registered\n",
bcon->name, bcon->index))
return;
/*
* before we register a new CON_BOOT console, make sure we don't
* already have a valid console
*/
if (console_drivers && newcon->flags & CON_BOOT) {
/* find the last or real console */
for_each_console(bcon) {
if (!(bcon->flags & CON_BOOT)) {
pr_info("Too late to register bootconsole %s%d\n",
newcon->name, newcon->index);
return;
}
}
}
if (console_drivers && console_drivers->flags & CON_BOOT)
bcon = console_drivers;
if (preferred_console < 0 || bcon || !console_drivers)
preferred_console = selected_console;
if (newcon->early_setup)
newcon->early_setup();
/*
* See if we want to use this console driver. If we
* didn't select a console we take the first one
* that registers here.
*/
if (preferred_console < 0) {
if (newcon->index < 0)
newcon->index = 0;
if (newcon->setup == NULL ||
newcon->setup(newcon, NULL) == 0) {
newcon->flags |= CON_ENABLED;
if (newcon->device) {
newcon->flags |= CON_CONSDEV;
preferred_console = 0;
}
}
}
/*
* See if this console matches one we selected on
* the command line.
*/
for (i = 0, c = console_cmdline;
i < MAX_CMDLINECONSOLES && c->name[0];
i++, c++) {
BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
if (strcmp(c->name, newcon->name) != 0)
continue;
if (newcon->index >= 0 &&
newcon->index != c->index)
continue;
if (newcon->index < 0)
newcon->index = c->index;
if (_braille_register_console(newcon, c))
return;
if (newcon->setup &&
newcon->setup(newcon, console_cmdline[i].options) != 0)
break;
newcon->flags |= CON_ENABLED;
if (i == selected_console) {
newcon->flags |= CON_CONSDEV;
preferred_console = selected_console;
}
break;
}
if (!(newcon->flags & CON_ENABLED))
return;
/*
* If we have a bootconsole, and are switching to a real console,
* don't print everything out again, since when the boot console, and
* the real console are the same physical device, it's annoying to
* see the beginning boot messages twice
*/
if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
newcon->flags &= ~CON_PRINTBUFFER;
/*
* Put this console in the list - keep the
* preferred driver at the head of the list.
*/
console_lock();
if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
newcon->next = console_drivers;
console_drivers = newcon;
if (newcon->next)
newcon->next->flags &= ~CON_CONSDEV;
} else {
newcon->next = console_drivers->next;
console_drivers->next = newcon;
}
if (newcon->flags & CON_EXTENDED)
if (!nr_ext_console_drivers++)
pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
if (newcon->flags & CON_PRINTBUFFER) {
/*
* console_unlock(); will print out the buffered messages
* for us.
*/
raw_spin_lock_irqsave(&logbuf_lock, flags);
console_seq = syslog_seq;
console_idx = syslog_idx;
console_prev = syslog_prev;
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
/*
* We're about to replay the log buffer. Only do this to the
* just-registered console to avoid excessive message spam to
* the already-registered consoles.
*/
exclusive_console = newcon;
}
console_unlock();
console_sysfs_notify();
/*
* By unregistering the bootconsoles after we enable the real console
* we get the "console xxx enabled" message on all the consoles -
* boot consoles, real consoles, etc - this is to ensure that end
* users know there might be something in the kernel's log buffer that
* went to the bootconsole (that they do not see on the real console)
*/
pr_info("%sconsole [%s%d] enabled\n",
(newcon->flags & CON_BOOT) ? "boot" : "" ,
newcon->name, newcon->index);
if (bcon &&
((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
!keep_bootcon) {
/* We need to iterate through all boot consoles, to make
* sure we print everything out, before we unregister them.
*/
for_each_console(bcon)
if (bcon->flags & CON_BOOT)
unregister_console(bcon);
}
}
EXPORT_SYMBOL(register_console);
int unregister_console(struct console *console)
{
struct console *a, *b;
int res;
pr_info("%sconsole [%s%d] disabled\n",
(console->flags & CON_BOOT) ? "boot" : "" ,
console->name, console->index);
res = _braille_unregister_console(console);
if (res)
return res;
res = 1;
console_lock();
if (console_drivers == console) {
console_drivers=console->next;
res = 0;
} else if (console_drivers) {
for (a=console_drivers->next, b=console_drivers ;
a; b=a, a=b->next) {
if (a == console) {
b->next = a->next;
res = 0;
break;
}
}
}
if (!res && (console->flags & CON_EXTENDED))
nr_ext_console_drivers--;
/*
* If this isn't the last console and it has CON_CONSDEV set, we
* need to set it on the next preferred console.
*/
if (console_drivers != NULL && console->flags & CON_CONSDEV)
console_drivers->flags |= CON_CONSDEV;
console->flags &= ~CON_ENABLED;
console_unlock();
console_sysfs_notify();
return res;
}
EXPORT_SYMBOL(unregister_console);
/*
* Some boot consoles access data that is in the init section and which will
* be discarded after the initcalls have been run. To make sure that no code
* will access this data, unregister the boot consoles in a late initcall.
*
* If for some reason, such as deferred probe or the driver being a loadable
* module, the real console hasn't registered yet at this point, there will
* be a brief interval in which no messages are logged to the console, which
* makes it difficult to diagnose problems that occur during this time.
*
* To mitigate this problem somewhat, only unregister consoles whose memory
* intersects with the init section. Note that code exists elsewhere to get
* rid of the boot console as soon as the proper console shows up, so there
* won't be side-effects from postponing the removal.
*/
static int __init printk_late_init(void)
{
struct console *con;
for_each_console(con) {
if (!keep_bootcon && con->flags & CON_BOOT) {
/*
* Make sure to unregister boot consoles whose data
* resides in the init section before the init section
* is discarded. Boot consoles whose data will stick
* around will automatically be unregistered when the
* proper console replaces them.
*/
if (init_section_intersects(con, sizeof(*con)))
unregister_console(con);
}
}
hotcpu_notifier(console_cpu_notify, 0);
return 0;
}
late_initcall(printk_late_init);
#if defined CONFIG_PRINTK
/*
* Prevent starting printk_kthread from start_kernel()->parse_args().
* It's not possible at this stage. Instead, do it via the initcall
* or a sysfs knob.
*/
static bool printk_kthread_can_run;
static int printk_kthread_func(void *data)
{
while (1) {
set_current_state(TASK_INTERRUPTIBLE);
if (!printk_kthread_need_flush_console)
schedule();
__set_current_state(TASK_RUNNING);
/*
* Avoid an infinite loop when console_unlock() cannot
* access consoles, e.g. because console_suspended is
* true. schedule(), someone else will print the messages
* from resume_console().
*/
printk_kthread_need_flush_console = false;
console_lock();
console_unlock();
}
return 0;
}
static int __init_printk_kthread(void)
{
struct task_struct *thread;
struct sched_param param = {
.sched_priority = MAX_RT_PRIO - 1,
};
if (!printk_kthread_can_run || printk_sync || printk_kthread)
return 0;
thread = kthread_run(printk_kthread_func, NULL, "printk");
if (IS_ERR(thread)) {
pr_err("printk: unable to create printing thread\n");
printk_sync = true;
return PTR_ERR(thread);
}
sched_setscheduler(thread, SCHED_FIFO, ¶m);
printk_kthread = thread;
return 0;
}
static int printk_sync_set(const char *val, const struct kernel_param *kp)
{
int ret;
ret = param_set_bool(val, kp);
if (ret)
return ret;
return __init_printk_kthread();
}
static const struct kernel_param_ops param_ops_printk_sync = {
.set = printk_sync_set,
.get = param_get_bool,
};
module_param_cb(synchronous, ¶m_ops_printk_sync, &printk_sync,
S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(synchronous, "make printing to console synchronous");
/*
* Init async printk via late_initcall, after core/arch/etc.
* initialization.
*/
static __init int init_printk_kthread(void)
{
printk_kthread_can_run = true;
return __init_printk_kthread();
}
late_initcall(init_printk_kthread);
/*
* Delayed printk version, for scheduler-internal messages:
*/
#define PRINTK_PENDING_WAKEUP 0x01
#define PRINTK_PENDING_OUTPUT 0x02
static DEFINE_PER_CPU(int, printk_pending);
static void wake_up_klogd_work_func(struct irq_work *irq_work)
{
int pending = __this_cpu_xchg(printk_pending, 0);
if (pending & PRINTK_PENDING_OUTPUT) {
if (can_printk_async()) {
wake_up_process(printk_kthread);
} else {
/*
* If trylock fails, someone else is doing
* the printing
*/
if (console_trylock())
console_unlock();
}
}
if (pending & PRINTK_PENDING_WAKEUP)
wake_up_interruptible(&log_wait);
}
static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
.func = wake_up_klogd_work_func,
.flags = IRQ_WORK_LAZY,
};
void wake_up_klogd(void)
{
preempt_disable();
if (waitqueue_active(&log_wait)) {
this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
}
preempt_enable();
}
int printk_deferred(const char *fmt, ...)
{
va_list args;
int r;
preempt_disable();
va_start(args, fmt);
r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
va_end(args);
__this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
preempt_enable();
return r;
}
/*
* printk rate limiting, lifted from the networking subsystem.
*
* This enforces a rate limit: not more than 10 kernel messages
* every 5s to make a denial-of-service attack impossible.
*/
DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
int __printk_ratelimit(const char *func)
{
return ___ratelimit(&printk_ratelimit_state, func);
}
EXPORT_SYMBOL(__printk_ratelimit);
/**
* printk_timed_ratelimit - caller-controlled printk ratelimiting
* @caller_jiffies: pointer to caller's state
* @interval_msecs: minimum interval between prints
*
* printk_timed_ratelimit() returns true if more than @interval_msecs
* milliseconds have elapsed since the last time printk_timed_ratelimit()
* returned true.
*/
bool printk_timed_ratelimit(unsigned long *caller_jiffies,
unsigned int interval_msecs)
{
unsigned long elapsed = jiffies - *caller_jiffies;
if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
return false;
*caller_jiffies = jiffies;
return true;
}
EXPORT_SYMBOL(printk_timed_ratelimit);
static DEFINE_SPINLOCK(dump_list_lock);
static LIST_HEAD(dump_list);
/**
* kmsg_dump_register - register a kernel log dumper.
* @dumper: pointer to the kmsg_dumper structure
*
* Adds a kernel log dumper to the system. The dump callback in the
* structure will be called when the kernel oopses or panics and must be
* set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
*/
int kmsg_dump_register(struct kmsg_dumper *dumper)
{
unsigned long flags;
int err = -EBUSY;
/* The dump callback needs to be set */
if (!dumper->dump)
return -EINVAL;
spin_lock_irqsave(&dump_list_lock, flags);
/* Don't allow registering multiple times */
if (!dumper->registered) {
dumper->registered = 1;
list_add_tail_rcu(&dumper->list, &dump_list);
err = 0;
}
spin_unlock_irqrestore(&dump_list_lock, flags);
return err;
}
EXPORT_SYMBOL_GPL(kmsg_dump_register);
/**
* kmsg_dump_unregister - unregister a kmsg dumper.
* @dumper: pointer to the kmsg_dumper structure
*
* Removes a dump device from the system. Returns zero on success and
* %-EINVAL otherwise.
*/
int kmsg_dump_unregister(struct kmsg_dumper *dumper)
{
unsigned long flags;
int err = -EINVAL;
spin_lock_irqsave(&dump_list_lock, flags);
if (dumper->registered) {
dumper->registered = 0;
list_del_rcu(&dumper->list);
err = 0;
}
spin_unlock_irqrestore(&dump_list_lock, flags);
synchronize_rcu();
return err;
}
EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
static bool always_kmsg_dump;
module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
/**
* kmsg_dump - dump kernel log to kernel message dumpers.
* @reason: the reason (oops, panic etc) for dumping
*
* Call each of the registered dumper's dump() callback, which can
* retrieve the kmsg records with kmsg_dump_get_line() or
* kmsg_dump_get_buffer().
*/
void kmsg_dump(enum kmsg_dump_reason reason)
{
struct kmsg_dumper *dumper;
unsigned long flags;
if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
return;
rcu_read_lock();
list_for_each_entry_rcu(dumper, &dump_list, list) {
if (dumper->max_reason && reason > dumper->max_reason)
continue;
/* initialize iterator with data about the stored records */
dumper->active = true;
raw_spin_lock_irqsave(&logbuf_lock, flags);
dumper->cur_seq = clear_seq;
dumper->cur_idx = clear_idx;
dumper->next_seq = log_next_seq;
dumper->next_idx = log_next_idx;
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
/* invoke dumper which will iterate over records */
dumper->dump(dumper, reason);
/* reset iterator */
dumper->active = false;
}
rcu_read_unlock();
}
/**
* kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
* @dumper: registered kmsg dumper
* @syslog: include the "<4>" prefixes
* @line: buffer to copy the line to
* @size: maximum size of the buffer
* @len: length of line placed into buffer
*
* Start at the beginning of the kmsg buffer, with the oldest kmsg
* record, and copy one record into the provided buffer.
*
* Consecutive calls will return the next available record moving
* towards the end of the buffer with the youngest messages.
*
* A return value of FALSE indicates that there are no more records to
* read.
*
* The function is similar to kmsg_dump_get_line(), but grabs no locks.
*/
bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
char *line, size_t size, size_t *len)
{
struct printk_log *msg;
size_t l = 0;
bool ret = false;
if (!dumper->active)
goto out;
if (dumper->cur_seq < log_first_seq) {
/* messages are gone, move to first available one */
dumper->cur_seq = log_first_seq;
dumper->cur_idx = log_first_idx;
}
/* last entry */
if (dumper->cur_seq >= log_next_seq)
goto out;
msg = log_from_idx(dumper->cur_idx);
l = msg_print_text(msg, 0, syslog, line, size);
dumper->cur_idx = log_next(dumper->cur_idx);
dumper->cur_seq++;
ret = true;
out:
if (len)
*len = l;
return ret;
}
/**
* kmsg_dump_get_line - retrieve one kmsg log line
* @dumper: registered kmsg dumper
* @syslog: include the "<4>" prefixes
* @line: buffer to copy the line to
* @size: maximum size of the buffer
* @len: length of line placed into buffer
*
* Start at the beginning of the kmsg buffer, with the oldest kmsg
* record, and copy one record into the provided buffer.
*
* Consecutive calls will return the next available record moving
* towards the end of the buffer with the youngest messages.
*
* A return value of FALSE indicates that there are no more records to
* read.
*/
bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
char *line, size_t size, size_t *len)
{
unsigned long flags;
bool ret;
raw_spin_lock_irqsave(&logbuf_lock, flags);
ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
/**
* kmsg_dump_get_buffer - copy kmsg log lines
* @dumper: registered kmsg dumper
* @syslog: include the "<4>" prefixes
* @buf: buffer to copy the line to
* @size: maximum size of the buffer
* @len: length of line placed into buffer
*
* Start at the end of the kmsg buffer and fill the provided buffer
* with as many of the the *youngest* kmsg records that fit into it.
* If the buffer is large enough, all available kmsg records will be
* copied with a single call.
*
* Consecutive calls will fill the buffer with the next block of
* available older records, not including the earlier retrieved ones.
*
* A return value of FALSE indicates that there are no more records to
* read.
*/
bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
char *buf, size_t size, size_t *len)
{
unsigned long flags;
u64 seq;
u32 idx;
u64 next_seq;
u32 next_idx;
enum log_flags prev;
size_t l = 0;
bool ret = false;
if (!dumper->active)
goto out;
raw_spin_lock_irqsave(&logbuf_lock, flags);
if (dumper->cur_seq < log_first_seq) {
/* messages are gone, move to first available one */
dumper->cur_seq = log_first_seq;
dumper->cur_idx = log_first_idx;
}
/* last entry */
if (dumper->cur_seq >= dumper->next_seq) {
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
goto out;
}
/* calculate length of entire buffer */
seq = dumper->cur_seq;
idx = dumper->cur_idx;
prev = 0;
while (seq < dumper->next_seq) {
struct printk_log *msg = log_from_idx(idx);
l += msg_print_text(msg, prev, true, NULL, 0);
idx = log_next(idx);
seq++;
prev = msg->flags;
}
/* move first record forward until length fits into the buffer */
seq = dumper->cur_seq;
idx = dumper->cur_idx;
prev = 0;
while (l > size && seq < dumper->next_seq) {
struct printk_log *msg = log_from_idx(idx);
l -= msg_print_text(msg, prev, true, NULL, 0);
idx = log_next(idx);
seq++;
prev = msg->flags;
}
/* last message in next interation */
next_seq = seq;
next_idx = idx;
l = 0;
while (seq < dumper->next_seq) {
struct printk_log *msg = log_from_idx(idx);
l += msg_print_text(msg, prev, syslog, buf + l, size - l);
idx = log_next(idx);
seq++;
prev = msg->flags;
}
dumper->next_seq = next_seq;
dumper->next_idx = next_idx;
ret = true;
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
out:
if (len)
*len = l;
return ret;
}
EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
/**
* kmsg_dump_rewind_nolock - reset the interator (unlocked version)
* @dumper: registered kmsg dumper
*
* Reset the dumper's iterator so that kmsg_dump_get_line() and
* kmsg_dump_get_buffer() can be called again and used multiple
* times within the same dumper.dump() callback.
*
* The function is similar to kmsg_dump_rewind(), but grabs no locks.
*/
void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
{
dumper->cur_seq = clear_seq;
dumper->cur_idx = clear_idx;
dumper->next_seq = log_next_seq;
dumper->next_idx = log_next_idx;
}
/**
* kmsg_dump_rewind - reset the interator
* @dumper: registered kmsg dumper
*
* Reset the dumper's iterator so that kmsg_dump_get_line() and
* kmsg_dump_get_buffer() can be called again and used multiple
* times within the same dumper.dump() callback.
*/
void kmsg_dump_rewind(struct kmsg_dumper *dumper)
{
unsigned long flags;
raw_spin_lock_irqsave(&logbuf_lock, flags);
kmsg_dump_rewind_nolock(dumper);
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
}
EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
static char dump_stack_arch_desc_str[128];
/**
* dump_stack_set_arch_desc - set arch-specific str to show with task dumps
* @fmt: printf-style format string
* @...: arguments for the format string
*
* The configured string will be printed right after utsname during task
* dumps. Usually used to add arch-specific system identifiers. If an
* arch wants to make use of such an ID string, it should initialize this
* as soon as possible during boot.
*/
void __init dump_stack_set_arch_desc(const char *fmt, ...)
{
va_list args;
va_start(args, fmt);
vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
fmt, args);
va_end(args);
}
/**
* dump_stack_print_info - print generic debug info for dump_stack()
* @log_lvl: log level
*
* Arch-specific dump_stack() implementations can use this function to
* print out the same debug information as the generic dump_stack().
*/
void dump_stack_print_info(const char *log_lvl)
{
printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
log_lvl, raw_smp_processor_id(), current->pid, current->comm,
print_tainted(), init_utsname()->release,
(int)strcspn(init_utsname()->version, " "),
init_utsname()->version);
if (dump_stack_arch_desc_str[0] != '\0')
printk("%sHardware name: %s\n",
log_lvl, dump_stack_arch_desc_str);
print_worker_info(log_lvl, current);
}
/**
* show_regs_print_info - print generic debug info for show_regs()
* @log_lvl: log level
*
* show_regs() implementations can use this function to print out generic
* debug information.
*/
void show_regs_print_info(const char *log_lvl)
{
dump_stack_print_info(log_lvl);
printk("%stask: %p ti: %p task.ti: %p\n",
log_lvl, current, current_thread_info(),
task_thread_info(current));
}
#endif
next prev parent reply other threads:[~2016-07-12 14:12 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-01 16:59 [Query] Preemption (hogging) of the work handler Viresh Kumar
2016-07-01 17:22 ` Tejun Heo
2016-07-01 17:28 ` Viresh Kumar
2016-07-06 18:28 ` Viresh Kumar
2016-07-06 19:23 ` Steven Rostedt
2016-07-06 19:25 ` Viresh Kumar
2016-07-11 10:26 ` Jan Kara
2016-07-11 15:44 ` Sergey Senozhatsky
2016-07-11 22:35 ` Viresh Kumar
2016-07-11 22:44 ` Rafael J. Wysocki
2016-07-11 22:46 ` Viresh Kumar
2016-07-12 12:24 ` Rafael J. Wysocki
2016-07-12 13:02 ` Viresh Kumar
2016-07-12 13:56 ` Petr Mladek
2016-07-12 14:04 ` Viresh Kumar
2016-07-12 9:38 ` Sergey Senozhatsky
2016-07-12 12:52 ` Petr Mladek
2016-07-12 13:12 ` Viresh Kumar
2016-07-12 17:11 ` Viresh Kumar
2016-07-12 19:59 ` Rafael J. Wysocki
2016-07-12 20:08 ` Viresh Kumar
2016-07-13 7:00 ` Sergey Senozhatsky
2016-07-13 12:05 ` Rafael J. Wysocki
2016-07-13 12:57 ` Sergey Senozhatsky
2016-07-13 13:22 ` Rafael J. Wysocki
2016-07-12 14:03 ` Sergey Senozhatsky
2016-07-12 14:12 ` Viresh Kumar [this message]
2016-07-14 23:52 ` Viresh Kumar
2016-07-15 13:11 ` Sergey Senozhatsky
2016-07-15 15:57 ` Viresh Kumar
2016-07-12 23:19 ` Viresh Kumar
2016-07-13 0:18 ` Viresh Kumar
2016-07-13 5:45 ` Sergey Senozhatsky
2016-07-13 15:39 ` Viresh Kumar
2016-07-13 23:08 ` Rafael J. Wysocki
2016-07-13 23:18 ` Viresh Kumar
2016-07-13 23:38 ` Greg Kroah-Hartman
2016-07-14 0:55 ` Sergey Senozhatsky
2016-07-14 1:09 ` Rafael J. Wysocki
2016-07-14 1:32 ` Sergey Senozhatsky
2016-07-14 21:57 ` Viresh Kumar
2016-07-14 21:55 ` Viresh Kumar
2016-07-14 14:12 ` Jan Kara
2016-07-14 14:33 ` Rafael J. Wysocki
2016-07-14 14:39 ` Jan Kara
2016-07-14 14:47 ` Rafael J. Wysocki
2016-07-14 14:55 ` Jan Kara
2016-07-14 22:14 ` Viresh Kumar
2016-07-14 14:34 ` Sergey Senozhatsky
2016-07-14 15:03 ` Jan Kara
2016-07-14 22:12 ` Viresh Kumar
2016-07-18 11:01 ` Jan Kara
2016-07-18 11:49 ` Rafael J. Wysocki
2016-07-29 20:42 ` Viresh Kumar
2016-07-30 2:12 ` Sergey Senozhatsky
2016-07-11 19:03 ` Viresh Kumar
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