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Commit a0f1ccfd authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds
Browse files

[PATCH] lockdep: do not recurse in printk 



Make printk()-ing from within the lock validation code safer by using the
lockdep-recursion counter.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 3047e99e

kernel/printk.c

+18 −5
Original line number Original line Diff line number Diff line
@@ -518,7 +518,9 @@ asmlinkage int vprintk(const char *fmt, va_list args) 
		zap_locks();

		zap_locks();





	/* This stops the holder of console_sem just where we want him */

	/* This stops the holder of console_sem just where we want him */

	spin_lock_irqsave(&logbuf_lock, flags);

	local_irq_save(flags);

	lockdep_off();

	spin_lock(&logbuf_lock);

	printk_cpu = smp_processor_id();

	printk_cpu = smp_processor_id();





	/* Emit the output into the temporary buffer */

	/* Emit the output into the temporary buffer */
@@ -588,7 +590,7 @@ asmlinkage int vprintk(const char *fmt, va_list args) 
		 */

		 */

		console_locked = 1;

		console_locked = 1;

		printk_cpu = UINT_MAX;

		printk_cpu = UINT_MAX;

		spin_unlock_irqrestore(&logbuf_lock, flags);

		spin_unlock(&logbuf_lock);





		/*

		/*

		 * Console drivers may assume that per-cpu resources have

		 * Console drivers may assume that per-cpu resources have
@@ -604,6 +606,8 @@ asmlinkage int vprintk(const char *fmt, va_list args) 
			console_locked = 0;

			console_locked = 0;

			up(&console_sem);

			up(&console_sem);

		}

		}

		lockdep_on();

		local_irq_restore(flags);

	} else {

	} else {

		/*

		/*

		 * Someone else owns the drivers.  We drop the spinlock, which

		 * Someone else owns the drivers.  We drop the spinlock, which
@@ -611,7 +615,9 @@ asmlinkage int vprintk(const char *fmt, va_list args) 
		 * console drivers with the output which we just produced.

		 * console drivers with the output which we just produced.

		 */

		 */

		printk_cpu = UINT_MAX;

		printk_cpu = UINT_MAX;

		spin_unlock_irqrestore(&logbuf_lock, flags);

		spin_unlock(&logbuf_lock);

		lockdep_on();

		local_irq_restore(flags);

	}

	}





	preempt_enable();

	preempt_enable();
@@ -809,9 +815,16 @@ void release_console_sem(void) 
	console_may_schedule = 0;

	console_may_schedule = 0;

	up(&console_sem);

	up(&console_sem);

	spin_unlock_irqrestore(&logbuf_lock, flags);

	spin_unlock_irqrestore(&logbuf_lock, flags);

	if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))

	if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait)) {

		/*

		 * If we printk from within the lock dependency code,

		 * from within the scheduler code, then do not lock

		 * up due to self-recursion:

		 */

		if (!lockdep_internal())

			wake_up_interruptible(&log_wait);

			wake_up_interruptible(&log_wait);

	}

	}

}

EXPORT_SYMBOL(release_console_sem);

EXPORT_SYMBOL(release_console_sem);





/**

/**