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rcutorture: Properly synchronize with OOM notifier 

The current rcutorture forward-progress code assumes that it is the
only cause of out-of-memory (OOM) events.  For script-based rcutorture
testing, this assumption is in fact correct.  However, testing based
on modprobe/rmmod might well encounter external OOM events, which could
happen at any time.

This commit therefore properly synchronizes the interaction between
rcutorture's forward-progress testing and its OOM notifier by adding a
global mutex.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2020-07-20 08:34:07 -07:00
parent c8fa637147
commit 57f602022e
1 changed files with 13 additions and 1 deletions
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14
kernel/rcu/rcutorture.c
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@ -1796,6 +1796,7 @@ struct rcu_fwd {
unsigned long rcu_launder_gp_seq_start;
};
static DEFINE_MUTEX(rcu_fwd_mutex);
static struct rcu_fwd *rcu_fwds;
static bool rcu_fwd_emergency_stop;
@ -2062,8 +2063,14 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
static int rcutorture_oom_notify(struct notifier_block *self,
unsigned long notused, void *nfreed)
{
struct rcu_fwd *rfp = rcu_fwds;
struct rcu_fwd *rfp;
mutex_lock(&rcu_fwd_mutex);
rfp = rcu_fwds;
if (!rfp) {
mutex_unlock(&rcu_fwd_mutex);
return NOTIFY_OK;
}
WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
__func__);
rcu_torture_fwd_cb_hist(rfp);
@ -2081,6 +2088,7 @@ static int rcutorture_oom_notify(struct notifier_block *self,
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__);
mutex_unlock(&rcu_fwd_mutex);
return NOTIFY_OK;
}
@ -2148,7 +2156,9 @@ static int __init rcu_torture_fwd_prog_init(void)
return -ENOMEM;
spin_lock_init(&rfp->rcu_fwd_lock);
rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
mutex_lock(&rcu_fwd_mutex);
rcu_fwds = rfp;
mutex_unlock(&rcu_fwd_mutex);
return torture_create_kthread(rcu_torture_fwd_prog, rfp, fwd_prog_task);
}
@ -2158,7 +2168,9 @@ static void rcu_torture_fwd_prog_cleanup(void)
torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
rfp = rcu_fwds;
mutex_lock(&rcu_fwd_mutex);
rcu_fwds = NULL;
mutex_unlock(&rcu_fwd_mutex);
kfree(rfp);
}