From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-fsdevel@vger.kernel.org,
John Ogness <jogness@linutronix.de>
Subject: [PATCH printk v3 03/40] printk: Convert console_drivers list to hlist
Date: Mon, 7 Nov 2022 15:22:01 +0106 [thread overview]
Message-ID: <20221107141638.3790965-4-john.ogness@linutronix.de> (raw)
In-Reply-To: <20221107141638.3790965-1-john.ogness@linutronix.de>
From: Thomas Gleixner <tglx@linutronix.de>
Replace the open coded single linked list with a hlist so a conversion
to SRCU protected list walks can reuse the existing primitives.
Co-developed-by: John Ogness <jogness@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
---
fs/proc/consoles.c | 3 +-
include/linux/console.h | 8 ++--
kernel/printk/printk.c | 101 ++++++++++++++++++++++------------------
3 files changed, 62 insertions(+), 50 deletions(-)
diff --git a/fs/proc/consoles.c b/fs/proc/consoles.c
index dfe6ce3505ce..cf2e0788f9c7 100644
--- a/fs/proc/consoles.c
+++ b/fs/proc/consoles.c
@@ -74,8 +74,9 @@ static void *c_start(struct seq_file *m, loff_t *pos)
static void *c_next(struct seq_file *m, void *v, loff_t *pos)
{
struct console *con = v;
+
++*pos;
- return con->next;
+ return hlist_entry_safe(con->node.next, struct console, node);
}
static void c_stop(struct seq_file *m, void *v)
diff --git a/include/linux/console.h b/include/linux/console.h
index 8c1686e2c233..7b5f21f9e469 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -15,6 +15,7 @@
#define _LINUX_CONSOLE_H_ 1
#include <linux/atomic.h>
+#include <linux/list.h>
#include <linux/types.h>
struct vc_data;
@@ -154,14 +155,16 @@ struct console {
u64 seq;
unsigned long dropped;
void *data;
- struct console *next;
+ struct hlist_node node;
};
+extern struct hlist_head console_list;
+
/*
* for_each_console() allows you to iterate on each console
*/
#define for_each_console(con) \
- for (con = console_drivers; con != NULL; con = con->next)
+ hlist_for_each_entry(con, &console_list, node)
extern int console_set_on_cmdline;
extern struct console *early_console;
@@ -174,7 +177,6 @@ enum con_flush_mode {
extern int add_preferred_console(char *name, int idx, char *options);
extern void register_console(struct console *);
extern int unregister_console(struct console *);
-extern struct console *console_drivers;
extern void console_lock(void);
extern int console_trylock(void);
extern void console_unlock(void);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index e4f1e7478b52..e6f0832e71f0 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -79,13 +79,12 @@ 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.
+ * console_sem protects console_list and console->flags updates, and also
+ * provides serialization for access to the entire console driver system.
*/
static DEFINE_SEMAPHORE(console_sem);
-struct console *console_drivers;
-EXPORT_SYMBOL_GPL(console_drivers);
+HLIST_HEAD(console_list);
+EXPORT_SYMBOL_GPL(console_list);
/*
* System may need to suppress printk message under certain
@@ -2556,7 +2555,7 @@ static int console_cpu_notify(unsigned int cpu)
* 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.
+ * exclusive access to the console system and console_list.
*
* Can sleep, returns nothing.
*/
@@ -2576,7 +2575,7 @@ 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.
+ * access to the console system and console_list.
*
* returns 1 on success, and 0 on failure to acquire the lock.
*/
@@ -2940,11 +2939,20 @@ void console_flush_on_panic(enum con_flush_mode mode)
console_may_schedule = 0;
if (mode == CONSOLE_REPLAY_ALL) {
+ struct hlist_node *tmp;
struct console *c;
u64 seq;
seq = prb_first_valid_seq(prb);
- for_each_console(c)
+ /*
+ * This cannot use for_each_console() because it's not established
+ * that the current context has console locked and neither there is
+ * a guarantee that there is no concurrency in that case.
+ *
+ * Open code it for documentation purposes and pretend that
+ * it works.
+ */
+ hlist_for_each_entry_safe(c, tmp, &console_list, node)
c->seq = seq;
}
console_unlock();
@@ -3081,6 +3089,9 @@ static void try_enable_default_console(struct console *newcon)
(con->flags & CON_BOOT) ? "boot" : "", \
con->name, con->index, ##__VA_ARGS__)
+#define console_first() \
+ hlist_entry(console_list.first, struct console, node)
+
/*
* The console driver calls this routine during kernel initialization
* to register the console printing procedure with printk() and to
@@ -3140,8 +3151,8 @@ void register_console(struct console *newcon)
* flag set and will be first in the list.
*/
if (preferred_console < 0) {
- if (!console_drivers || !console_drivers->device ||
- console_drivers->flags & CON_BOOT) {
+ if (hlist_empty(&console_list) || !console_first()->device ||
+ console_first()->flags & CON_BOOT) {
try_enable_default_console(newcon);
}
}
@@ -3169,20 +3180,22 @@ void register_console(struct console *newcon)
}
/*
- * Put this console in the list - keep the
- * preferred driver at the head of the list.
+ * 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;
- /* Ensure this flag is always set for the head of the list */
+ if (hlist_empty(&console_list)) {
+ /* Ensure CON_CONSDEV is always set for the head. */
newcon->flags |= CON_CONSDEV;
+ hlist_add_head(&newcon->node, &console_list);
+
+ } else if (newcon->flags & CON_CONSDEV) {
+ /* Only the new head can have CON_CONSDEV set. */
+ console_first()->flags &= ~CON_CONSDEV;
+ hlist_add_head(&newcon->node, &console_list);
+
} else {
- newcon->next = console_drivers->next;
- console_drivers->next = newcon;
+ hlist_add_behind(&newcon->node, console_list.first);
}
newcon->dropped = 0;
@@ -3209,16 +3222,18 @@ void register_console(struct console *newcon)
if (bootcon_enabled &&
((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
!keep_bootcon) {
- for_each_console(con)
+ struct hlist_node *tmp;
+
+ hlist_for_each_entry_safe(con, tmp, &console_list, node) {
if (con->flags & CON_BOOT)
unregister_console(con);
+ }
}
}
EXPORT_SYMBOL(register_console);
int unregister_console(struct console *console)
{
- struct console *con;
int res;
con_printk(KERN_INFO, console, "disabled\n");
@@ -3229,32 +3244,30 @@ int unregister_console(struct console *console)
if (res > 0)
return 0;
- res = -ENODEV;
console_lock();
- if (console_drivers == console) {
- console_drivers=console->next;
- res = 0;
- } else {
- for_each_console(con) {
- if (con->next == console) {
- con->next = console->next;
- res = 0;
- break;
- }
- }
+
+ /* Disable it unconditionally */
+ console->flags &= ~CON_ENABLED;
+
+ if (hlist_unhashed(&console->node)) {
+ console_unlock();
+ return -ENODEV;
}
- if (res)
- goto out_disable_unlock;
+ hlist_del_init(&console->node);
/*
+ * <HISTORICAL>
* If this isn't the last console and it has CON_CONSDEV set, we
* need to set it on the next preferred console.
+ * </HISTORICAL>
+ *
+ * The above makes no sense as there is no guarantee that the next
+ * console has any device attached. Oh well....
*/
- if (console_drivers != NULL && console->flags & CON_CONSDEV)
- console_drivers->flags |= CON_CONSDEV;
+ if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV)
+ console_first()->flags |= CON_CONSDEV;
- console->flags &= ~CON_ENABLED;
console_unlock();
console_sysfs_notify();
@@ -3262,12 +3275,6 @@ int unregister_console(struct console *console)
res = console->exit(console);
return res;
-
-out_disable_unlock:
- console->flags &= ~CON_ENABLED;
- console_unlock();
-
- return res;
}
EXPORT_SYMBOL(unregister_console);
@@ -3317,10 +3324,11 @@ void __init console_init(void)
*/
static int __init printk_late_init(void)
{
+ struct hlist_node *tmp;
struct console *con;
int ret;
- for_each_console(con) {
+ hlist_for_each_entry_safe(con, tmp, &console_list, node) {
if (!(con->flags & CON_BOOT))
continue;
@@ -3340,6 +3348,7 @@ static int __init printk_late_init(void)
unregister_console(con);
}
}
+
ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL,
console_cpu_notify);
WARN_ON(ret < 0);
--
2.30.2
next prev parent reply other threads:[~2022-11-07 14:16 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-07 14:15 [PATCH printk v3 00/40] reduce console_lock scope John Ogness
2022-11-07 14:15 ` [PATCH printk v3 01/40] rcu: implement lockdep_rcu_enabled for !CONFIG_DEBUG_LOCK_ALLOC John Ogness
2022-11-07 18:01 ` Paul E. McKenney
2022-11-07 19:23 ` John Ogness
2022-11-08 19:27 ` Paul E. McKenney
2022-11-09 17:49 ` Paul E. McKenney
2022-11-08 10:29 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 02/40] serial: kgdboc: Lock console list in probe function John Ogness
2022-11-09 8:20 ` Daniel Thompson
2022-11-07 14:16 ` John Ogness [this message]
2022-11-07 14:16 ` [PATCH printk v3 04/40] printk: Prepare for SRCU console list protection John Ogness
2022-11-08 12:14 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 05/40] printk: fix setting first seq for consoles John Ogness
2022-11-08 12:20 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 06/40] um: kmsg_dump: only dump when no output console available John Ogness
2022-11-08 12:41 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 07/40] console: introduce console_is_enabled() wrapper John Ogness
2022-11-08 16:18 ` Petr Mladek
2022-11-10 15:05 ` John Ogness
2022-11-11 13:32 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 08/40] printk: use console_is_enabled() John Ogness
2022-11-08 17:40 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 09/40] um: kmsg_dump: " John Ogness
2022-11-09 14:52 ` Petr Mladek
2022-11-09 14:56 ` Petr Mladek
2022-11-09 14:57 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 10/40] kdb: kdb_io: " John Ogness
2022-11-09 8:22 ` Daniel Thompson
2022-11-09 14:59 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 11/40] um: kmsg_dumper: use srcu console list iterator John Ogness
2022-11-09 15:05 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 12/40] tty: serial: kgdboc: document console_lock usage John Ogness
2022-11-09 8:23 ` Daniel Thompson
2022-11-09 15:19 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 13/40] tty: tty_io: " John Ogness
2022-11-09 15:20 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 14/40] proc: consoles: " John Ogness
2022-11-09 15:22 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 15/40] kdb: use srcu console list iterator John Ogness
2022-11-09 8:53 ` Daniel Thompson
2022-11-09 9:27 ` John Ogness
2022-11-09 15:27 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 16/40] printk: console_flush_all: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 17/40] printk: console_unblank: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 18/40] printk: console_flush_on_panic: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 19/40] printk: console_device: " John Ogness
2022-11-09 15:58 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 20/40] printk: __pr_flush: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 21/40] printk: introduce console_list_lock John Ogness
2022-11-10 12:58 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 22/40] console: introduce console_is_registered() John Ogness
2022-11-10 13:00 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 23/40] serial_core: replace uart_console_enabled() with uart_console_registered() John Ogness
2022-11-08 8:46 ` Geert Uytterhoeven
2022-11-10 13:24 ` Petr Mladek
2022-11-10 13:46 ` John Ogness
2022-11-07 14:16 ` [PATCH printk v3 24/40] tty: nfcon: use console_is_registered() John Ogness
2022-11-08 8:39 ` Geert Uytterhoeven
2022-11-10 13:58 ` Petr Mladek
2022-11-10 14:19 ` John Ogness
2022-11-10 17:50 ` Eero Tamminen
2022-11-07 14:16 ` [PATCH printk v3 25/40] efi: earlycon: " John Ogness
2022-11-10 14:28 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 26/40] tty: hvc: " John Ogness
2022-11-10 14:52 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 27/40] tty: serial: earlycon: " John Ogness
2022-11-10 15:00 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 28/40] tty: serial: pic32_uart: " John Ogness
2022-11-10 15:01 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 29/40] tty: serial: samsung_tty: " John Ogness
2022-11-10 15:01 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 30/40] tty: serial: xilinx_uartps: " John Ogness
2022-11-10 15:04 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 31/40] usb: early: xhci-dbc: " John Ogness
2022-11-10 15:05 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 32/40] netconsole: avoid CON_ENABLED misuse to track registration John Ogness
2022-11-10 15:17 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 33/40] printk, xen: fbfront: create/use safe function for forcing preferred John Ogness
2022-11-10 15:34 ` Petr Mladek
2022-11-10 16:03 ` John Ogness
2022-11-10 17:26 ` Petr Mladek
2022-11-10 22:37 ` John Ogness
2022-11-11 10:48 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 34/40] tty: tty_io: use console_list_lock for list synchronization John Ogness
2022-11-07 14:16 ` [PATCH printk v3 35/40] proc: consoles: use console_list_lock for list iteration John Ogness
2022-11-07 14:16 ` [PATCH printk v3 36/40] tty: serial: kgdboc: use console_list_lock for list traversal John Ogness
2022-11-09 9:06 ` Daniel Thompson
2022-11-09 9:44 ` John Ogness
2022-11-10 18:00 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 37/40] tty: serial: kgdboc: synchronize tty_find_polling_driver() and register_console() John Ogness
2022-11-10 15:13 ` Daniel Thompson
2022-11-10 18:03 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 38/40] tty: serial: kgdboc: use console_list_lock to trap exit John Ogness
2022-11-10 15:18 ` Daniel Thompson
2022-11-11 9:59 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 39/40] printk: relieve console_lock of list synchronization duties John Ogness
2022-11-07 16:30 ` John Ogness
2022-11-11 10:27 ` Petr Mladek
2022-11-11 13:06 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 40/40] tty: serial: sh-sci: use setup() callback for early console John Ogness
2022-11-08 8:53 ` Geert Uytterhoeven
2022-11-11 17:15 ` Petr Mladek
2022-11-11 14:43 ` [PATCH printk v3 00/40] reduce console_lock scope Mathieu Desnoyers
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