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| author | John Ogness <john.ogness@linutronix.de> | 2023-07-17 21:46:03 +0200 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2023-07-20 13:06:22 +0200 |
| commit | 51a1d258e50e03a0216bf42b6af9ff34ec402ac1 (patch) | |
| tree | 4ee8e6c60cb6b01cce664a7e6f802031b6268ac3 /kernel/printk/printk.c | |
| parent | printk: Reduce console_unblank() usage in unsafe scenarios (diff) | |
| download | linux-51a1d258e50e03a0216bf42b6af9ff34ec402ac1.tar.xz linux-51a1d258e50e03a0216bf42b6af9ff34ec402ac1.zip | |
printk: Keep non-panic-CPUs out of console lock
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
Diffstat (limited to 'kernel/printk/printk.c')
| -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 7aa9dbee12e8..7219991885e6 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2583,6 +2583,25 @@ 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 - block the console subsystem from printing * @@ -2595,6 +2614,10 @@ 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; @@ -2613,6 +2636,9 @@ 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) { @@ -2632,25 +2658,6 @@ 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. * |