Commit-ID: 2667ccce9328e4e25ed77a83291c066d5e11e65a
Gitweb: https://git.kernel.org/tip/2667ccce9328e4e25ed77a83291c066d5e11e65a
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxx>
AuthorDate: Fri, 5 Oct 2018 09:09:49 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxx>
CommitDate: Sat, 1 Dec 2018 12:45:41 -0800
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@xxxxxxxxxxxxx>
---
kernel/rcu/rcutorture.c | 60 ++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 49 insertions(+), 11 deletions(-)
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 080b5ac6340c..afa98162575d 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -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;
}
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