Re: [PATCH v3] rcu: Dump all rcuc kthreads status for CPUs that not report quiescent state
From: Dan Carpenter
Date: Mon Apr 25 2022 - 09:24:46 EST
Hi Zqiang,
url: https://github.com/intel-lab-lkp/linux/commits/Zqiang/rcu-Dump-all-rcuc-kthreads-status-for-CPUs-that-not-report-quiescent-state/20220424-121850
base: https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev
config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive/20220424/202204241503.imwh5SqZ-lkp@xxxxxxxxx/config)
compiler: gcc-11 (Debian 11.2.0-20) 11.2.0
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
smatch warnings:
kernel/rcu/tree_stall.h:467 print_cpu_stall_info() error: uninitialized symbol 'j'.
vim +/j +467 kernel/rcu/tree_stall.h
59b73a27681c58 Paul E. McKenney 2019-01-11 440 static void print_cpu_stall_info(int cpu)
59b73a27681c58 Paul E. McKenney 2019-01-11 441 {
59b73a27681c58 Paul E. McKenney 2019-01-11 442 unsigned long delta;
88375825171c7d Paul E. McKenney 2020-03-31 443 bool falsepositive;
59b73a27681c58 Paul E. McKenney 2019-01-11 444 struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
59b73a27681c58 Paul E. McKenney 2019-01-11 445 char *ticks_title;
59b73a27681c58 Paul E. McKenney 2019-01-11 446 unsigned long ticks_value;
17d9de741a1aaf Zqiang 2022-04-24 447 bool rcuc_starved;
17d9de741a1aaf Zqiang 2022-04-24 448 unsigned long j;
59b73a27681c58 Paul E. McKenney 2019-01-11 449
59b73a27681c58 Paul E. McKenney 2019-01-11 450 /*
59b73a27681c58 Paul E. McKenney 2019-01-11 451 * We could be printing a lot while holding a spinlock. Avoid
59b73a27681c58 Paul E. McKenney 2019-01-11 452 * triggering hard lockup.
59b73a27681c58 Paul E. McKenney 2019-01-11 453 */
59b73a27681c58 Paul E. McKenney 2019-01-11 454 touch_nmi_watchdog();
59b73a27681c58 Paul E. McKenney 2019-01-11 455
59b73a27681c58 Paul E. McKenney 2019-01-11 456 ticks_value = rcu_seq_ctr(rcu_state.gp_seq - rdp->gp_seq);
59b73a27681c58 Paul E. McKenney 2019-01-11 457 if (ticks_value) {
59b73a27681c58 Paul E. McKenney 2019-01-11 458 ticks_title = "GPs behind";
59b73a27681c58 Paul E. McKenney 2019-01-11 459 } else {
59b73a27681c58 Paul E. McKenney 2019-01-11 460 ticks_title = "ticks this GP";
59b73a27681c58 Paul E. McKenney 2019-01-11 461 ticks_value = rdp->ticks_this_gp;
59b73a27681c58 Paul E. McKenney 2019-01-11 462 }
59b73a27681c58 Paul E. McKenney 2019-01-11 463 delta = rcu_seq_ctr(rdp->mynode->gp_seq - rdp->rcu_iw_gp_seq);
88375825171c7d Paul E. McKenney 2020-03-31 464 falsepositive = rcu_is_gp_kthread_starving(NULL) &&
88375825171c7d Paul E. McKenney 2020-03-31 465 rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp));
17d9de741a1aaf Zqiang 2022-04-24 466 rcuc_starved = rcu_is_rcuc_kthread_starving(rdp, &j);
That tree has some new returns in rcu_is_rcuc_kthread_starving() where
*jp is not set.
17d9de741a1aaf Zqiang 2022-04-24 @467 pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%03x/%ld/%#lx softirq=%u/%u fqs=%ld rcuc=%ld jiffies(%s) %s\n",
59b73a27681c58 Paul E. McKenney 2019-01-11 468 cpu,
59b73a27681c58 Paul E. McKenney 2019-01-11 469 "O."[!!cpu_online(cpu)],
59b73a27681c58 Paul E. McKenney 2019-01-11 470 "o."[!!(rdp->grpmask & rdp->mynode->qsmaskinit)],
59b73a27681c58 Paul E. McKenney 2019-01-11 471 "N."[!!(rdp->grpmask & rdp->mynode->qsmaskinitnext)],
59b73a27681c58 Paul E. McKenney 2019-01-11 472 !IS_ENABLED(CONFIG_IRQ_WORK) ? '?' :
59b73a27681c58 Paul E. McKenney 2019-01-11 473 rdp->rcu_iw_pending ? (int)min(delta, 9UL) + '0' :
59b73a27681c58 Paul E. McKenney 2019-01-11 474 "!."[!delta],
59b73a27681c58 Paul E. McKenney 2019-01-11 475 ticks_value, ticks_title,
59b73a27681c58 Paul E. McKenney 2019-01-11 476 rcu_dynticks_snap(rdp) & 0xfff,
59b73a27681c58 Paul E. McKenney 2019-01-11 477 rdp->dynticks_nesting, rdp->dynticks_nmi_nesting,
59b73a27681c58 Paul E. McKenney 2019-01-11 478 rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
88375825171c7d Paul E. McKenney 2020-03-31 479 data_race(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,
17d9de741a1aaf Zqiang 2022-04-24 480 j, rcuc_starved ? "starved" : "",
88375825171c7d Paul E. McKenney 2020-03-31 481 falsepositive ? " (false positive?)" : "");
59b73a27681c58 Paul E. McKenney 2019-01-11 482 }
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