diff options
| author | John Ogness | 2023-07-17 21:52:03 +0206 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2023-09-23 11:11:07 +0200 |
| commit | 13ebf3ff08b046fc798dc82a42d73713cb03eded (patch) | |
| tree | 9c7d704fba514efdecb574d1e61c8ff0c35a3033 /kernel/printk | |
| parent | ee42bfc791aa3cd78e29046f26a09d189beb3efb (diff) | |
printk: Keep non-panic-CPUs out of console lock
[ Upstream commit 51a1d258e50e03a0216bf42b6af9ff34ec402ac1 ]
When in a panic situation, non-panic CPUs should avoid holding the
console lock so as not to contend with the panic CPU. This is already
implemented with abandon_console_lock_in_panic(), which is checked
after each printed line. However, non-panic CPUs should also avoid
trying to acquire the console lock during a panic.
Modify console_trylock() to fail and console_lock() to block() when
called from a non-panic CPU during a panic.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20230717194607.145135-4-john.ogness@linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel/printk')
| -rw-r--r-- | kernel/printk/printk.c | 45 |
1 files changed, 26 insertions, 19 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index e4f1e7478b52..4b9429f3fd6d 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2552,6 +2552,25 @@ static int console_cpu_notify(unsigned int cpu) return 0; } +/* + * Return true when this CPU should unlock console_sem without pushing all + * messages to the console. This reduces the chance that the console is + * locked when the panic CPU tries to use it. + */ +static bool abandon_console_lock_in_panic(void) +{ + if (!panic_in_progress()) + return false; + + /* + * We can use raw_smp_processor_id() here because it is impossible for + * the task to be migrated to the panic_cpu, or away from it. If + * panic_cpu has already been set, and we're not currently executing on + * that CPU, then we never will be. + */ + return atomic_read(&panic_cpu) != raw_smp_processor_id(); +} + /** * console_lock - lock the console system for exclusive use. * @@ -2564,6 +2583,10 @@ void console_lock(void) { might_sleep(); + /* On panic, the console_lock must be left to the panic cpu. */ + while (abandon_console_lock_in_panic()) + msleep(1000); + down_console_sem(); if (console_suspended) return; @@ -2582,6 +2605,9 @@ EXPORT_SYMBOL(console_lock); */ int console_trylock(void) { + /* On panic, the console_lock must be left to the panic cpu. */ + if (abandon_console_lock_in_panic()) + return 0; if (down_trylock_console_sem()) return 0; if (console_suspended) { @@ -2601,25 +2627,6 @@ int is_console_locked(void) EXPORT_SYMBOL(is_console_locked); /* - * Return true when this CPU should unlock console_sem without pushing all - * messages to the console. This reduces the chance that the console is - * locked when the panic CPU tries to use it. - */ -static bool abandon_console_lock_in_panic(void) -{ - if (!panic_in_progress()) - return false; - - /* - * We can use raw_smp_processor_id() here because it is impossible for - * the task to be migrated to the panic_cpu, or away from it. If - * panic_cpu has already been set, and we're not currently executing on - * that CPU, then we never will be. - */ - return atomic_read(&panic_cpu) != raw_smp_processor_id(); -} - -/* * Check if the given console is currently capable and allowed to print * records. * |