Commit bd0b7dc4 authored by Ye Weihua's avatar Ye Weihua
Browse files

printk: avoid deadlock in panic 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I991OV



--------------------------------

In the process of load testing against panic, a deadlock issue
was discovered. The reason is that in the panic process,
console_unlock doesn't handle the printk_context variable
evenly, causing printk_context to overflow downwards, allowing
vprintk_func to enter the nmi direct branch without disabling
interrupt. Upon holding the logbuf_lock lock, an interrupt
running wake_up_klogd_work_func was called, resulting in a
deadlock.

To avoid this issue, move printk_safe_ext_irqrestore after
check abandon_console_lock_in_panic().

Fixes: 7c2aff38 ([Backport] printk: Drop console_sem during panic)
Signed-off-by: default avatarYe Weihua <yeweihua4@huawei.com>
parent 32bb7b0a

kernel/printk/printk.c

+2 −2
Original line number Diff line number Diff line
@@ -2609,12 +2609,12 @@ void console_unlock(void) 
			return;

		}



		printk_safe_exit_irqrestore(flags);



		/* Allow panic_cpu to take over the consoles safely */

		if (abandon_console_lock_in_panic())

			break;



		printk_safe_exit_irqrestore(flags);



		if (do_cond_resched)

			cond_resched();

	}