diff options
| author | John Ogness <john.ogness@linutronix.de> | 2024-12-09 12:23:46 +0106 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2024-12-16 13:26:31 +0100 |
| commit | 0161e2d6950fe66cf6ac1c10d945bae971f33667 (patch) | |
| tree | e12087793cfe89c62446951321929beeb03ae651 /kernel/printk/printk.c | |
| parent | f1c21cf470595c4561d4671fd499af94152175d5 (diff) | |
printk: Defer legacy printing when holding printk_cpu_sync
The documentation of printk_cpu_sync_get() clearly states
that the owner must never perform any activities where it waits
for a CPU. For legacy printing there can be spinning on the
console_lock and on the port lock. Therefore legacy printing
must be deferred when holding the printk_cpu_sync.
Note that in the case of emergency states, atomic consoles
are not prevented from printing when printk is deferred. This
is appropriate because they do not spin-wait indefinitely for
other CPUs.
Reported-by: Rik van Riel <riel@surriel.com>
Closes: https://lore.kernel.org/r/20240715232052.73eb7fb1@imladris.surriel.com
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Fixes: 55d6af1d6688 ("lib/nmi_backtrace: explicitly serialize banner and regs")
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20241209111746.192559-3-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
Diffstat (limited to 'kernel/printk/printk.c')
| -rw-r--r-- | kernel/printk/printk.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 80910bc3470c..f446a06b4da8 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -4922,6 +4922,11 @@ void console_try_replay_all(void) static atomic_t printk_cpu_sync_owner = ATOMIC_INIT(-1); static atomic_t printk_cpu_sync_nested = ATOMIC_INIT(0); +bool is_printk_cpu_sync_owner(void) +{ + return (atomic_read(&printk_cpu_sync_owner) == raw_smp_processor_id()); +} + /** * __printk_cpu_sync_wait() - Busy wait until the printk cpu-reentrant * spinning lock is not owned by any CPU. |