From: Stephen Brennan stephen.s.brennan@oracle.com
mainline inclusion from mainline-v5.18-rc1 commit 8ebc476fd51e6c0fd3174ec1959a20ba99d4c5e5 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I89RYC CVE: NA
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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.c...
Conflict: kernel/printk/printk.c
Signed-off-by: Ye Weihua yeweihua4@huawei.com --- kernel/printk/printk.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 765c4fd9c5d0..f52eceb3c48a 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2375,6 +2375,25 @@ static int have_callable_console(void) 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(); +} + /* * Can we actually use the console at this time on this cpu? * @@ -2522,6 +2541,10 @@ void console_unlock(void)
printk_safe_exit_irqrestore(flags);
+ /* Allow panic_cpu to take over the consoles safely */ + if (abandon_console_lock_in_panic()) + break; + if (do_cond_resched) cond_resched(); } @@ -2543,7 +2566,7 @@ void console_unlock(void) raw_spin_unlock(&logbuf_lock); printk_safe_exit_irqrestore(flags);
- if (retry && console_trylock()) + if (retry && !abandon_console_lock_in_panic() && console_trylock()) goto again; } EXPORT_SYMBOL(console_unlock);