From 7412dc6d55eed6b76180e40ac3601412ebde29bd Mon Sep 17 00:00:00 2001 From: John Ogness Date: Wed, 7 Feb 2024 14:47:03 +0106 Subject: dump_stack: Do not get cpu_sync for panic CPU dump_stack() is called in panic(). If for some reason another CPU is holding the printk_cpu_sync and is unable to release it, the panic CPU will be unable to continue and print the stacktrace. Since non-panic CPUs are not allowed to store new printk messages anyway, there is no need to synchronize the stacktrace output in a panic situation. For the panic CPU, do not get the printk_cpu_sync because it is not needed and avoids a potential deadlock scenario in panic(). Link: https://lore.kernel.org/lkml/ZcIGKU8sxti38Kok@alley Signed-off-by: John Ogness Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20240207134103.1357162-15-john.ogness@linutronix.de Signed-off-by: Petr Mladek --- lib/dump_stack.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) (limited to 'lib') diff --git a/lib/dump_stack.c b/lib/dump_stack.c index 83471e81501a7..222c6d6c8281a 100644 --- a/lib/dump_stack.c +++ b/lib/dump_stack.c @@ -96,15 +96,25 @@ static void __dump_stack(const char *log_lvl) */ asmlinkage __visible void dump_stack_lvl(const char *log_lvl) { + bool in_panic = this_cpu_in_panic(); unsigned long flags; /* * Permit this cpu to perform nested stack dumps while serialising - * against other CPUs + * against other CPUs, unless this CPU is in panic. + * + * When in panic, non-panic CPUs are not permitted to store new + * printk messages so there is no need to synchronize the output. + * This avoids potential deadlock in panic() if another CPU is + * holding and unable to release the printk_cpu_sync. */ - printk_cpu_sync_get_irqsave(flags); + if (!in_panic) + printk_cpu_sync_get_irqsave(flags); + __dump_stack(log_lvl); - printk_cpu_sync_put_irqrestore(flags); + + if (!in_panic) + printk_cpu_sync_put_irqrestore(flags); } EXPORT_SYMBOL(dump_stack_lvl); -- cgit 1.2.3-korg