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Commit 2667ccce authored by Paul E. McKenney's avatar Paul E. McKenney
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rcutorture: Recover from OOM during forward-progress tests 



This commit causes the OOM handler to do rcu_barrier() calls and to
free up forward-progress callbacks in order to recover from OOM events.
The current test is terminated, but subsequent forward-progress tests can
proceed.  This allows a long test to result in multiple forward-progress
failures, greatly reducing the required testing time.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent 73d665b1

kernel/rcu/rcutorture.c

+49 −11
Original line number Diff line number Diff line
@@ -1649,13 +1649,14 @@ static void rcu_torture_fwd_cb_hist(void) 
/* Callback function for continuous-flood RCU callbacks. */

static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)

{

	unsigned long flags;

	int i;

	struct rcu_fwd_cb *rfcp = container_of(rhp, struct rcu_fwd_cb, rh);

	struct rcu_fwd_cb **rfcpp;



	rfcp->rfc_next = NULL;

	rfcp->rfc_gps++;

	spin_lock(&rcu_fwd_lock);

	spin_lock_irqsave(&rcu_fwd_lock, flags);

	rfcpp = rcu_fwd_cb_tail;

	rcu_fwd_cb_tail = &rfcp->rfc_next;

	WRITE_ONCE(*rfcpp, rfcp);
@@ -1664,7 +1665,33 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp) 
	if (i >= ARRAY_SIZE(n_launders_hist))

		i = ARRAY_SIZE(n_launders_hist) - 1;

	n_launders_hist[i]++;

	spin_unlock(&rcu_fwd_lock);

	spin_unlock_irqrestore(&rcu_fwd_lock, flags);

}



/*

 * Free all callbacks on the rcu_fwd_cb_head list, either because the

 * test is over or because we hit an OOM event.

 */

static unsigned long rcu_torture_fwd_prog_cbfree(void)

{

	unsigned long flags;

	unsigned long freed = 0;

	struct rcu_fwd_cb *rfcp;



	for (;;) {

		spin_lock_irqsave(&rcu_fwd_lock, flags);

		rfcp = rcu_fwd_cb_head;

		if (!rfcp)

			break;

		rcu_fwd_cb_head = rfcp->rfc_next;

		if (!rcu_fwd_cb_head)

			rcu_fwd_cb_tail = &rcu_fwd_cb_head;

		spin_unlock_irqrestore(&rcu_fwd_lock, flags);

		kfree(rfcp);

		freed++;

	}

	spin_unlock_irqrestore(&rcu_fwd_lock, flags);

	return freed;

}



/* Carry out need_resched()/cond_resched() forward-progress testing. */
@@ -1743,6 +1770,9 @@ static void rcu_torture_fwd_prog_cr(void) 
	unsigned long stopat;

	unsigned long stoppedat;



	if (READ_ONCE(rcu_fwd_emergency_stop))

		return; /* Get out of the way quickly, no GP wait! */



	/* Loop continuously posting RCU callbacks. */

	WRITE_ONCE(rcu_fwd_cb_nodelay, true);

	cur_ops->sync(); /* Later readers see above write. */
@@ -1788,16 +1818,10 @@ static void rcu_torture_fwd_prog_cr(void) 
	cver = READ_ONCE(rcu_torture_current_version) - cver;

	gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);

	cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */

	for (;;) {

		rfcp = rcu_fwd_cb_head;

		if (!rfcp)

			break;

		rcu_fwd_cb_head = rfcp->rfc_next;

		kfree(rfcp);

	}

	rcu_fwd_cb_tail = &rcu_fwd_cb_head;

	(void)rcu_torture_fwd_prog_cbfree();



	WRITE_ONCE(rcu_fwd_cb_nodelay, false);

	if (!torture_must_stop()) {

	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",

			 __func__,
@@ -1817,9 +1841,23 @@ static void rcu_torture_fwd_prog_cr(void) 
static int rcutorture_oom_notify(struct notifier_block *self,

				 unsigned long notused, void *nfreed)

{

	WARN(1, "%s invoked upon OOM during forward-progress testing.\n",

	     __func__);

	rcu_torture_fwd_cb_hist();

	rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rcu_fwd_startat) / 2));

	WRITE_ONCE(rcu_fwd_emergency_stop, true);

	smp_mb(); /* Emergency stop before free and wait to avoid hangs. */

	pr_info("%s: Freed %lu RCU callbacks.\n",

		__func__, rcu_torture_fwd_prog_cbfree());

	rcu_barrier();

	pr_info("%s: Freed %lu RCU callbacks.\n",

		__func__, rcu_torture_fwd_prog_cbfree());

	rcu_barrier();

	pr_info("%s: Freed %lu RCU callbacks.\n",

		__func__, rcu_torture_fwd_prog_cbfree());

	smp_mb(); /* Frees before return to avoid redoing OOM. */

	(*(unsigned long *)nfreed)++; /* Forward progress CBs freed! */

	pr_info("%s returning after OOM processing.\n", __func__);

	return NOTIFY_OK;

}