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Commit bd8d7cf5 authored by Jan Kara's avatar Jan Kara Committed by Linus Torvalds
Browse files

printk: fix lockdep instrumentation of console_sem 



Printk calls mutex_acquire() / mutex_release() by hand to instrument
lockdep about console_sem.  However in some corner cases the
instrumentation is missing.  Fix the problem by creating helper functions
for locking / unlocking console_sem which take care of lockdep
instrumentation as well.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Reported-by: default avatarFabio Estevam <festevam@gmail.com>
Reported-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: default avatarFabio Estevam <fabio.estevam@freescale.com>
Tested-By: default avatarValdis Kletnieks <valdis.kletnieks@vt.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 608873ca

kernel/printk/printk.c

+32 −14
Original line number Diff line number Diff line
@@ -90,6 +90,29 @@ static struct lockdep_map console_lock_dep_map = { 
};

#endif



/*

 * Helper macros to handle lockdep when locking/unlocking console_sem. We use

 * macros instead of functions so that _RET_IP_ contains useful information.

 */

#define down_console_sem() do { \

	down(&console_sem);\

	mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\

} while (0)



static int __down_trylock_console_sem(unsigned long ip)

{

	if (down_trylock(&console_sem))

		return 1;

	mutex_acquire(&console_lock_dep_map, 0, 1, ip);

	return 0;

}

#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)



#define up_console_sem() do { \

	mutex_release(&console_lock_dep_map, 1, _RET_IP_);\

	up(&console_sem);\

} while (0)



/*

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

 * keeping track if we have the console semaphore held. It's
@@ -1422,7 +1445,7 @@ static int console_trylock_for_printk(unsigned int cpu) 
	 */

	if (!can_use_console(cpu)) {

		console_locked = 0;

		up(&console_sem);

		up_console_sem();

		return 0;

	}

	return 1;
@@ -1951,16 +1974,14 @@ void suspend_console(void) 
	printk("Suspending console(s) (use no_console_suspend to debug)\n");

	console_lock();

	console_suspended = 1;

	up(&console_sem);

	mutex_release(&console_lock_dep_map, 1, _RET_IP_);

	up_console_sem();

}



void resume_console(void)

{

	if (!console_suspend_enabled)

		return;

	down(&console_sem);

	mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);

	down_console_sem();

	console_suspended = 0;

	console_unlock();

}
@@ -2002,12 +2023,11 @@ void console_lock(void) 
{

	might_sleep();



	down(&console_sem);

	down_console_sem();

	if (console_suspended)

		return;

	console_locked = 1;

	console_may_schedule = 1;

	mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);

}

EXPORT_SYMBOL(console_lock);
@@ -2021,15 +2041,14 @@ EXPORT_SYMBOL(console_lock); 
 */

int console_trylock(void)

{

	if (down_trylock(&console_sem))

	if (down_trylock_console_sem())

		return 0;

	if (console_suspended) {

		up(&console_sem);

		up_console_sem();

		return 0;

	}

	console_locked = 1;

	console_may_schedule = 0;

	mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);

	return 1;

}

EXPORT_SYMBOL(console_trylock);
@@ -2091,7 +2110,7 @@ void console_unlock(void) 
	bool retry;



	if (console_suspended) {

		up(&console_sem);

		up_console_sem();

		return;

	}
@@ -2153,7 +2172,6 @@ skip: 
		local_irq_restore(flags);

	}

	console_locked = 0;

	mutex_release(&console_lock_dep_map, 1, _RET_IP_);



	/* Release the exclusive_console once it is used */

	if (unlikely(exclusive_console))
@@ -2161,7 +2179,7 @@ skip: 


	raw_spin_unlock(&logbuf_lock);



	up(&console_sem);

	up_console_sem();



	/*

	 * Someone could have filled up the buffer again, so re-check if there's
@@ -2206,7 +2224,7 @@ void console_unblank(void) 
	 * oops_in_progress is set to 1..

	 */

	if (oops_in_progress) {

		if (down_trylock(&console_sem) != 0)

		if (down_trylock_console_sem() != 0)

			return;

	} else

		console_lock();