From: Paul E. McKenney Date: Mon, 10 Feb 2025 14:59:24 +0000 (-0800) Subject: rcutorture: Complain if an ->up_read() is delayed more than 10 seconds X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=62d92c9b87db43cc255411fe2827b9de42fa0523;p=thirdparty%2Flinux.git rcutorture: Complain if an ->up_read() is delayed more than 10 seconds The down/up SRCU reader testing uses an hrtimer handler to exit the SRCU read-side critical section. This might be delayed, and if delayed for too long, it can prevent the rcutorture run from completing. This commit therefore complains if the hrtimer handler is delayed for more than ten seconds. [ paulmck, joel: Apply kernel test robot feedback to avoid false-positive complaint of excessive ->up_read() delays by using HRTIMER_MODE_HARD ] Tested-by: kernel test robot Signed-off-by: Paul E. McKenney Signed-off-by: Joel Fernandes Signed-off-by: Neeraj Upadhyay (AMD) --- diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 13cf0e4728689..22288efc8c673 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -2447,6 +2447,8 @@ rcu_torture_reader(void *arg) struct rcu_torture_one_read_state_updown { struct hrtimer rtorsu_hrt; bool rtorsu_inuse; + ktime_t rtorsu_kt; + unsigned long rtorsu_j; struct torture_random_state rtorsu_trs; struct rcu_torture_one_read_state rtorsu_rtors; }; @@ -2485,7 +2487,7 @@ static int rcu_torture_updown_init(void) for (i = 0; i < n_up_down; i++) { init_rcu_torture_one_read_state(&updownreaders[i].rtorsu_rtors, rand); hrtimer_setup(&updownreaders[i].rtorsu_hrt, rcu_torture_updown_hrt, CLOCK_MONOTONIC, - HRTIMER_MODE_REL | HRTIMER_MODE_SOFT); + HRTIMER_MODE_REL | HRTIMER_MODE_HARD); torture_random_init(&updownreaders[i].rtorsu_trs); init_rcu_torture_one_read_state(&updownreaders[i].rtorsu_rtors, &updownreaders[i].rtorsu_trs); @@ -2533,7 +2535,10 @@ static void rcu_torture_updown_one(struct rcu_torture_one_read_state_updown *rto t = torture_random(&rtorsup->rtorsu_trs) & 0xfffff; // One per million. if (t < 10 * 1000) t = 200 * 1000 * 1000; - hrtimer_start(&rtorsup->rtorsu_hrt, t, HRTIMER_MODE_REL | HRTIMER_MODE_SOFT); + hrtimer_start(&rtorsup->rtorsu_hrt, t, HRTIMER_MODE_REL | HRTIMER_MODE_HARD); + smp_mb(); // Sample jiffies after posting hrtimer. + rtorsup->rtorsu_j = jiffies; // Not used by hrtimer handler. + rtorsup->rtorsu_kt = t; } /* @@ -2544,6 +2549,7 @@ static void rcu_torture_updown_one(struct rcu_torture_one_read_state_updown *rto static int rcu_torture_updown(void *arg) { + unsigned long j; struct rcu_torture_one_read_state_updown *rtorsup; VERBOSE_TOROUT_STRING("rcu_torture_updown task started"); @@ -2551,8 +2557,12 @@ rcu_torture_updown(void *arg) for (rtorsup = updownreaders; rtorsup < &updownreaders[n_up_down]; rtorsup++) { if (torture_must_stop()) break; - if (smp_load_acquire(&rtorsup->rtorsu_inuse)) + j = smp_load_acquire(&jiffies); // Time before ->rtorsu_inuse. + if (smp_load_acquire(&rtorsup->rtorsu_inuse)) { + WARN_ONCE(time_after(j, rtorsup->rtorsu_j + 1 + HZ * 10), + "hrtimer queued at jiffies %lu for %lld ns took %lu jiffies\n", rtorsup->rtorsu_j, rtorsup->rtorsu_kt, j - rtorsup->rtorsu_j); continue; + } rcu_torture_updown_one(rtorsup); } torture_hrtimeout_ms(1, 1000, &rcu_torture_updown_rand);