Unverified Commit 366d48f9 authored by openeuler-ci-bot's avatar openeuler-ci-bot Committed by Gitee
Browse files

!2492 Avoid spin or livelock during panic 

Merge Pull Request from: @ci-robot 
 
PR sync from: Ye Weihua <yeweihua4@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/YEWC6BDONDZD6JN77ICGV4EMGXC2JOJ6/ 
Stephen Brennan (4):
  printk: Add panic_in_progress helper
  printk: disable optimistic spin during panic
  printk: Avoid livelock with heavy printk during panic
  printk: Drop console_sem during panic


-- 
2.34.1
 
https://gitee.com/openeuler/kernel/issues/I89RYC 
 
Link:https://gitee.com/openeuler/kernel/pulls/2492

 

Reviewed-by: default avatarXu Kuohai <xukuohai@huawei.com>
Signed-off-by: default avatarJialin Zhang <zhangjialin11@huawei.com>
parents 5fe7bd3f 7c2aff38

kernel/printk/printk.c

+54 −1
Original line number Original line Diff line number Diff line
@@ -93,6 +93,12 @@ EXPORT_SYMBOL_GPL(console_drivers); 
 */

 */

int __read_mostly suppress_printk;

int __read_mostly suppress_printk;





/*

 * During panic, heavy printk by other CPUs can delay the

 * panic and risk deadlock on console resources.

 */

int __read_mostly suppress_panic_printk;



#ifdef CONFIG_LOCKDEP

#ifdef CONFIG_LOCKDEP

static struct lockdep_map console_lock_dep_map = {

static struct lockdep_map console_lock_dep_map = {

	.name = "console_lock"

	.name = "console_lock"
@@ -258,6 +264,11 @@ static void __up_console_sem(unsigned long ip) 
}

}

#define up_console_sem() __up_console_sem(_RET_IP_)

#define up_console_sem() __up_console_sem(_RET_IP_)





static bool panic_in_progress(void)

{

	return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID);

}



/*

/*

 * This is used for debugging the mess that is the VT code by

 * This is used for debugging the mess that is the VT code by

 * keeping track if we have the console semaphore held. It's

 * keeping track if we have the console semaphore held. It's
@@ -1846,6 +1857,16 @@ static int console_trylock_spinning(void) 
	if (console_trylock())

	if (console_trylock())

		return 1;

		return 1;





	/*

	 * It's unsafe to spin once a panic has begun. If we are the

	 * panic CPU, we may have already halted the owner of the

	 * console_sem. If we are not the panic CPU, then we should

	 * avoid taking console_sem, so the panic CPU has a better

	 * chance of cleanly acquiring it later.

	 */

	if (panic_in_progress())

		return 0;



	printk_safe_enter_irqsave(flags);

	printk_safe_enter_irqsave(flags);





	raw_spin_lock(&console_owner_lock);

	raw_spin_lock(&console_owner_lock);
@@ -2045,6 +2066,10 @@ asmlinkage int vprintk_emit(int facility, int level, 
	if (unlikely(suppress_printk))

	if (unlikely(suppress_printk))

		return 0;

		return 0;





	if (unlikely(suppress_panic_printk) &&

	    atomic_read(&panic_cpu) != raw_smp_processor_id())

		return 0;



	if (level == LOGLEVEL_SCHED) {

	if (level == LOGLEVEL_SCHED) {

		level = LOGLEVEL_DEFAULT;

		level = LOGLEVEL_DEFAULT;

		in_sched = true;

		in_sched = true;
@@ -2419,6 +2444,25 @@ static int have_callable_console(void) 
	return 0;

	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?

 * Can we actually use the console at this time on this cpu?

 *

 *
@@ -2449,6 +2493,7 @@ void console_unlock(void) 
{

{

	static char ext_text[CONSOLE_EXT_LOG_MAX];

	static char ext_text[CONSOLE_EXT_LOG_MAX];

	static char text[LOG_LINE_MAX + PREFIX_MAX];

	static char text[LOG_LINE_MAX + PREFIX_MAX];

	static int panic_console_dropped;

	unsigned long flags;

	unsigned long flags;

	bool do_cond_resched, retry;

	bool do_cond_resched, retry;

	struct printk_info info;

	struct printk_info info;
@@ -2503,6 +2548,10 @@ void console_unlock(void) 
		if (console_seq != r.info->seq) {

		if (console_seq != r.info->seq) {

			console_dropped += r.info->seq - console_seq;

			console_dropped += r.info->seq - console_seq;

			console_seq = r.info->seq;

			console_seq = r.info->seq;

			if (panic_in_progress() && panic_console_dropped++ > 10) {

				suppress_panic_printk = 1;

				pr_warn_once("Too many dropped messages. Supress message on non-panic CPUs to prevent livelock.\n");

			}

		}

		}





		if (suppress_message_printing(r.info->level)) {

		if (suppress_message_printing(r.info->level)) {
@@ -2560,6 +2609,10 @@ void console_unlock(void) 




		printk_safe_exit_irqrestore(flags);

		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)

		if (do_cond_resched)

			cond_resched();

			cond_resched();

	}

	}
@@ -2581,7 +2634,7 @@ void console_unlock(void) 
	raw_spin_unlock(&logbuf_lock);

	raw_spin_unlock(&logbuf_lock);

	printk_safe_exit_irqrestore(flags);

	printk_safe_exit_irqrestore(flags);





	if (retry && console_trylock())

	if (retry && !abandon_console_lock_in_panic() && console_trylock())

		goto again;

		goto again;

}

}

EXPORT_SYMBOL(console_unlock);

EXPORT_SYMBOL(console_unlock);