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authorPaul E. McKenney <paulmck@kernel.org>2021-12-28 15:59:38 -0800
committerPaul E. McKenney <paulmck@kernel.org>2022-02-01 17:24:39 -0800
commit89440d2dad0cc2a781290470cb90402ebba481fc (patch)
treeae1f9173e91043d0849844e8be545d086ca8254f /kernel/rcu/rcutorture.c
parent02b51a1cf47977d8772c7dcc363ef6a1e6e59f21 (diff)
rcutorture: Fix rcu_fwd_mutex deadlock
The rcu_torture_fwd_cb_hist() function acquires rcu_fwd_mutex, but is invoked from rcutorture_oom_notify() function, which hold this same mutex across this call. This commit fixes the resulting deadlock. Reported-by: kernel test robot <oliver.sang@intel.com> Tested-by: Oliver Sang <oliver.sang@intel.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu/rcutorture.c')
-rw-r--r--kernel/rcu/rcutorture.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index e99658efd97f..1c8f40b90f70 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2180,7 +2180,6 @@ static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
for (i = ARRAY_SIZE(rfp->n_launders_hist) - 1; i > 0; i--)
if (rfp->n_launders_hist[i].n_launders > 0)
break;
- mutex_lock(&rcu_fwd_mutex); // Serialize histograms.
pr_alert("%s: Callback-invocation histogram %d (duration %lu jiffies):",
__func__, rfp->rcu_fwd_id, jiffies - rfp->rcu_fwd_startat);
gps_old = rfp->rcu_launder_gp_seq_start;
@@ -2193,7 +2192,6 @@ static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
gps_old = gps;
}
pr_cont("\n");
- mutex_unlock(&rcu_fwd_mutex);
}
/* Callback function for continuous-flood RCU callbacks. */
@@ -2431,7 +2429,9 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
n_launders, n_launders_sa,
n_max_gps, n_max_cbs, cver, gps);
atomic_long_add(n_max_cbs, &rcu_fwd_max_cbs);
+ mutex_lock(&rcu_fwd_mutex); // Serialize histograms.
rcu_torture_fwd_cb_hist(rfp);
+ mutex_unlock(&rcu_fwd_mutex);
}
schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
tick_dep_clear_task(current, TICK_DEP_BIT_RCU);

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