From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org
Subject: [PATCH next v2 2/3] printk: change @clear_seq to atomic64_t
Date: Tue, 1 Dec 2020 21:59:40 +0106 [thread overview]
Message-ID: <20201201205341.3871-3-john.ogness@linutronix.de> (raw)
In-Reply-To: <20201201205341.3871-1-john.ogness@linutronix.de>
Currently @clear_seq access is protected by @logbuf_lock. Once
@logbuf_lock is removed some other form of synchronization will be
required. Change the type of @clear_seq to atomic64_t to provide the
synchronization.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
kernel/printk/printk.c | 22 ++++++++++++++--------
1 file changed, 14 insertions(+), 8 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index fc5e3a7d6d89..e9018c4e1b66 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -403,7 +403,7 @@ static u64 exclusive_console_stop_seq;
static unsigned long console_dropped;
/* the next printk record to read after the last 'clear' command */
-static u64 clear_seq;
+static atomic64_t clear_seq = ATOMIC64_INIT(0);
#ifdef CONFIG_PRINTK_CALLER
#define PREFIX_MAX 48
@@ -797,7 +797,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
* like issued by 'dmesg -c'. Reading /dev/kmsg itself
* changes no global state, and does not clear anything.
*/
- user->seq = clear_seq;
+ user->seq = atomic64_read(&clear_seq);
break;
case SEEK_END:
/* after the last record */
@@ -914,6 +914,9 @@ void log_buf_vmcoreinfo_setup(void)
* parse it and detect any changes to structure down the line.
*/
+ VMCOREINFO_SIZE(atomic64_t);
+ VMCOREINFO_TYPE_OFFSET(atomic64_t, counter);
+
VMCOREINFO_STRUCT_SIZE(printk_ringbuffer);
VMCOREINFO_OFFSET(printk_ringbuffer, desc_ring);
VMCOREINFO_OFFSET(printk_ringbuffer, text_data_ring);
@@ -1476,6 +1479,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
struct printk_info info;
unsigned int line_count;
struct printk_record r;
+ u64 clr_seq;
char *text;
int len = 0;
u64 seq;
@@ -1487,15 +1491,17 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
time = printk_time;
logbuf_lock_irq();
+ clr_seq = atomic64_read(&clear_seq);
+
/*
* Find first record that fits, including all following records,
* into the user-provided buffer for this dump.
*/
- prb_for_each_info(clear_seq, prb, seq, &info, &line_count)
+ prb_for_each_info(clr_seq, prb, seq, &info, &line_count)
len += get_record_print_text_size(&info, line_count, true, time);
/* move first record forward until length fits into the buffer */
- prb_for_each_info(clear_seq, prb, seq, &info, &line_count) {
+ prb_for_each_info(clr_seq, prb, seq, &info, &line_count) {
if (len <= size)
break;
len -= get_record_print_text_size(&info, line_count, true, time);
@@ -1526,7 +1532,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
}
if (clear)
- clear_seq = seq;
+ atomic64_set(&clear_seq, seq);
logbuf_unlock_irq();
kfree(text);
@@ -1536,7 +1542,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
static void syslog_clear(void)
{
logbuf_lock_irq();
- clear_seq = prb_next_seq(prb);
+ atomic64_set(&clear_seq, prb_next_seq(prb));
logbuf_unlock_irq();
}
@@ -3205,7 +3211,7 @@ void kmsg_dump(enum kmsg_dump_reason reason)
dumper->active = true;
logbuf_lock_irqsave(flags);
- dumper->cur_seq = clear_seq;
+ dumper->cur_seq = atomic64_read(&clear_seq);
dumper->next_seq = prb_next_seq(prb);
logbuf_unlock_irqrestore(flags);
@@ -3412,7 +3418,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
*/
void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
{
- dumper->cur_seq = clear_seq;
+ dumper->cur_seq = atomic64_read(&clear_seq);
dumper->next_seq = prb_next_seq(prb);
}
--
2.20.1
next prev parent reply other threads:[~2020-12-01 20:54 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-01 20:53 [PATCH next v2 0/3] printk: remove logbuf_lock John Ogness
2020-12-01 20:53 ` [PATCH next v2 1/3] printk: inline log_output(),log_store() in vprintk_store() John Ogness
2020-12-03 15:57 ` Petr Mladek
2020-12-03 16:25 ` John Ogness
2020-12-04 6:13 ` Sergey Senozhatsky
2020-12-04 8:26 ` Petr Mladek
2020-12-01 20:53 ` John Ogness [this message]
2020-12-04 9:12 ` [PATCH next v2 2/3] printk: change @clear_seq to atomic64_t Petr Mladek
2020-12-06 20:23 ` John Ogness
2020-12-07 9:34 ` Peter Zijlstra
2020-12-07 10:03 ` John Ogness
2020-12-07 12:56 ` Peter Zijlstra
2020-12-07 12:56 ` Petr Mladek
2020-12-07 16:46 ` David Laight
2020-12-08 20:34 ` Sergey Senozhatsky
2020-12-08 22:30 ` John Ogness
2020-12-09 1:04 ` Sergey Senozhatsky
2020-12-09 8:16 ` Peter Zijlstra
2020-12-09 9:22 ` Sergey Senozhatsky
2020-12-09 10:46 ` Sergey Senozhatsky
2020-12-09 11:00 ` Peter Zijlstra
2020-12-09 11:28 ` Sergey Senozhatsky
2020-12-09 12:29 ` Peter Zijlstra
2020-12-09 8:07 ` Peter Zijlstra
2020-12-01 20:53 ` [PATCH next v2 3/3] printk: remove logbuf_lock, add syslog_lock John Ogness
2020-12-04 6:41 ` Sergey Senozhatsky
2020-12-06 20:44 ` John Ogness
2020-12-04 15:52 ` devkmsg: was " Petr Mladek
2020-12-06 20:51 ` John Ogness
2020-12-07 9:56 ` Petr Mladek
2020-12-04 15:57 ` syslog: was: " Petr Mladek
2020-12-06 21:06 ` John Ogness
2020-12-07 10:01 ` Petr Mladek
2020-12-04 16:10 ` recursion handling: " Petr Mladek
2020-12-05 4:25 ` Sergey Senozhatsky
2020-12-06 22:08 ` John Ogness
2020-12-05 9:41 ` Sergey Senozhatsky
2020-12-06 22:17 ` John Ogness
2020-12-06 21:44 ` John Ogness
2020-12-07 11:17 ` Petr Mladek
2020-12-04 16:15 ` vprintk_store: was: " Petr Mladek
2020-12-06 22:30 ` John Ogness
2020-12-07 12:46 ` Petr Mladek
2020-12-04 16:19 ` consoles: " Petr Mladek
2020-12-05 4:39 ` Sergey Senozhatsky
2020-12-07 9:50 ` Petr Mladek
2020-12-08 20:51 ` Sergey Senozhatsky
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