diff options
| author |   Stephen Brennan <stephen.s.brennan@oracle.com> | 2022-02-02 09:18:21 -0800 |
|---|---|---|
| committer |   Petr Mladek <pmladek@suse.com> | 2022-02-14 13:39:20 +0100 |
| commit | 8ebc476fd51e6c0fd3174ec1959a20ba99d4c5e5 (patch) | |
| tree | 793d63aff1ee802d00cf2155182b379570f76c4e /kernel/printk | |
| parent | printk: Avoid livelock with heavy printk during panic (diff) | |
| download | linux-dev-8ebc476fd51e6c0fd3174ec1959a20ba99d4c5e5.tar.xz linux-dev-8ebc476fd51e6c0fd3174ec1959a20ba99d4c5e5.zip | |
printk: Drop console_sem during panic
If another CPU is in panic, we are about to be halted. Try to gracefully
abandon the console_sem, leaving it free for the panic CPU to grab.
Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220202171821.179394-5-stephen.s.brennan@oracle.com
Diffstat (limited to 'kernel/printk')
| -rw-r--r-- | kernel/printk/printk.c | 25 |
1 files changed, 24 insertions, 1 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 2ec6b547cda6..6a51907a33b9 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2598,6 +2598,25 @@ static int have_callable_console(void) } /* + * 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(); +} + +/* * Can we actually use the console at this time on this cpu? * * Console drivers may assume that per-cpu resources have been allocated. So @@ -2745,6 +2764,10 @@ skip: if (handover) return; + /* Allow panic_cpu to take over the consoles safely */ + if (abandon_console_lock_in_panic()) + break; + if (do_cond_resched) cond_resched(); } @@ -2762,7 +2785,7 @@ skip: * flush, no worries. */ retry = prb_read_valid(prb, next_seq, NULL); - if (retry && console_trylock()) + if (retry && !abandon_console_lock_in_panic() && console_trylock()) goto again; } EXPORT_SYMBOL(console_unlock); |