Commit e8516c64 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Fix stutter_wait() return value and freelist checks 



The stutter_wait() function is supposed to return true if it actually
waits and false otherwise, but it instead unconditionally returns false.
Which hides a bug in rcu_torture_writer() that fails to account for
the fact that one of the rcu_tortures[] array elements will normally be
referenced by rcu_torture_current, and thus not be on the freelist.

This commit therefore corrects the stutter_wait() return value and adds a
check for rcu_torture_current to rcu_torture_writer()'s check that things
get freed after everything goes quiescent.  In addition, this commit
causes torture_stutter() to give a bit more than one second (instead of
only one jiffy) warning of the end of the stutter interval.  Finally,
this commit disables long-delay readers and aggressive update-side
forward-progress checks while forward-progress testing is in flight.

Reported-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent 140e53f2

kernel/rcu/rcutorture.c

+12 −4
Original line number Diff line number Diff line
@@ -1010,10 +1010,13 @@ rcu_torture_writer(void *arg) 
				       !rcu_gp_is_normal();

		}

		rcu_torture_writer_state = RTWS_STUTTER;

		if (stutter_wait("rcu_torture_writer"))

		if (stutter_wait("rcu_torture_writer") &&

		    !READ_ONCE(rcu_fwd_cb_nodelay))

			for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)

				if (list_empty(&rcu_tortures[i].rtort_free))

					WARN_ON_ONCE(1);

				if (list_empty(&rcu_tortures[i].rtort_free) &&

				    rcu_access_pointer(rcu_torture_current) !=

				    &rcu_tortures[i])

					WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);

	} while (!torture_must_stop());

	/* Reset expediting back to unexpedited. */

	if (expediting > 0)
@@ -1709,6 +1712,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) 
	}



	/* Tight loop containing cond_resched(). */

	WRITE_ONCE(rcu_fwd_cb_nodelay, true);

	cur_ops->sync(); /* Later readers see above write. */

	if  (selfpropcb) {

		WRITE_ONCE(fcs.stop, 0);

		cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb);
@@ -1747,6 +1752,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) 
		WARN_ON(READ_ONCE(fcs.stop) != 2);

		destroy_rcu_head_on_stack(&fcs.rh);

	}

	schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */

	WRITE_ONCE(rcu_fwd_cb_nodelay, false);

}



/* Carry out call_rcu() forward-progress testing. */
@@ -1816,7 +1823,6 @@ static void rcu_torture_fwd_prog_cr(void) 
	cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */

	(void)rcu_torture_fwd_prog_cbfree();



	WRITE_ONCE(rcu_fwd_cb_nodelay, false);

	if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop)) {

		WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);

		pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n",
@@ -1827,6 +1833,8 @@ static void rcu_torture_fwd_prog_cr(void) 
			 n_max_gps, n_max_cbs, cver, gps);

		rcu_torture_fwd_cb_hist();

	}

	schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */

	WRITE_ONCE(rcu_fwd_cb_nodelay, false);

}

kernel/torture.c

+13 −4
Original line number Diff line number Diff line
@@ -578,10 +578,12 @@ static int stutter; 
bool stutter_wait(const char *title)

{

	int spt;

	bool ret = false;



	cond_resched_tasks_rcu_qs();

	spt = READ_ONCE(stutter_pause_test);

	for (; spt; spt = READ_ONCE(stutter_pause_test)) {

		ret = true;

		if (spt == 1) {

			schedule_timeout_interruptible(1);

		} else if (spt == 2) {
@@ -592,7 +594,7 @@ bool stutter_wait(const char *title) 
		}

		torture_shutdown_absorb(title);

	}

	return !!spt;

	return ret;

}

EXPORT_SYMBOL_GPL(stutter_wait);
@@ -602,13 +604,20 @@ EXPORT_SYMBOL_GPL(stutter_wait); 
 */

static int torture_stutter(void *arg)

{

	int wtime;



	VERBOSE_TOROUT_STRING("torture_stutter task started");

	do {

		if (!torture_must_stop() && stutter > 1) {

			wtime = stutter;

			if (stutter > HZ + 1) {

				WRITE_ONCE(stutter_pause_test, 1);

			schedule_timeout_interruptible(stutter - 1);

				wtime = stutter - HZ - 1;

				schedule_timeout_interruptible(wtime);

				wtime = HZ + 1;

			}

			WRITE_ONCE(stutter_pause_test, 2);

			schedule_timeout_interruptible(1);

			schedule_timeout_interruptible(wtime);

		}

		WRITE_ONCE(stutter_pause_test, 0);

		if (!torture_must_stop())

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