From: Paul E. McKenney Date: Tue, 28 Dec 2021 23:59:38 +0000 (-0800) Subject: rcutorture: Fix rcu_fwd_mutex deadlock X-Git-Tag: howlett/maple/20220722_2~1009^2^6~2 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=89440d2dad0cc2a781290470cb90402ebba481fc;p=users%2Fjedix%2Flinux-maple.git 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 Tested-by: Oliver Sang Signed-off-by: Paul E. McKenney --- 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);