Commit e3bdaefb authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Frederic Weisbecker
Browse files

locktorture: Add acq_writer_lim to complain about long acquistion times 



This commit adds a locktorture.acq_writer_lim module parameter that
specifies the maximum number of jiffies that is expected to be consumed
by write-side lock acquisition.  If this limit is exceeded, a WARN_ONCE()
causes a splat.  Note that this limit applies to the main lock acquisition
only, not to any nested acquisitions.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
parent 84cee9e7

kernel/locking/locktorture.c

+13 −2
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ 
MODULE_LICENSE("GPL");

MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");



torture_param(int, acq_writer_lim, 0, "Write_acquisition time limit (jiffies).");

torture_param(int, long_hold, 100, "Do occasional long hold of lock (ms), 0=disable");

torture_param(int, nested_locks, 0, "Number of nested locks (max = 8)");

torture_param(int, nreaders_stress, -1, "Number of read-locking stress-test threads");
@@ -852,11 +853,13 @@ static struct lock_torture_ops percpu_rwsem_lock_ops = { 
 */

static int lock_torture_writer(void *arg)

{

	unsigned long j;

	unsigned long j1;

	u32 lockset_mask;

	struct lock_stress_stats *lwsp = arg;

	int tid = lwsp - cxt.lwsa;

	DEFINE_TORTURE_RANDOM(rand);

	u32 lockset_mask;

	bool skip_main_lock;

	int tid = lwsp - cxt.lwsa;



	VERBOSE_TOROUT_STRING("lock_torture_writer task started");

	if (!rt_task(current))
@@ -883,12 +886,20 @@ static int lock_torture_writer(void *arg) 
			cxt.cur_ops->nested_lock(tid, lockset_mask);



		if (!skip_main_lock) {

			if (acq_writer_lim > 0)

				j = jiffies;

			cxt.cur_ops->writelock(tid);

			if (WARN_ON_ONCE(lock_is_write_held))

				lwsp->n_lock_fail++;

			lock_is_write_held = true;

			if (WARN_ON_ONCE(atomic_read(&lock_is_read_held)))

				lwsp->n_lock_fail++; /* rare, but... */

			if (acq_writer_lim > 0) {

				j1 = jiffies;

				WARN_ONCE(time_after(j1, j + acq_writer_lim),

					  "%s: Lock acquisition took %lu jiffies.\n",

					  __func__, j1 - j);

			}

			lwsp->n_lock_acquired++;



			cxt.cur_ops->write_delay(&rand);