diff options
Diffstat (limited to 'kernel/printk/printk.c')
| -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); |