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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: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-10-05 09:09:49 -07:00
parent 73d665b141
commit 2667ccce93
1 changed files with 49 additions and 11 deletions
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60
kernel/rcu/rcutorture.c
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@ -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;
}