tree: https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/next head: 31f76cdc284fc45751d88b5ed754630a5f8a8914 commit: 3f4013e60f5eaf15913143831cfa8b8a2e2fbcb5 [33/34] Squash with 7202bfecfbec ("rcu: Pretend ->boost_mtx acquired legitimately") config: i386-randconfig-x077-201740 (attached as .config) compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901 reproduce: git checkout 3f4013e60f5eaf15913143831cfa8b8a2e2fbcb5 # save the attached .config to linux build tree make ARCH=i386
All errors (new ones prefixed by >>):
In file included from kernel/rcu/tree.c:4279:0:
kernel/rcu/tree_plugin.h: In function 'rcu_read_unlock_special':
>> kernel/rcu/tree_plugin.h:533:4: error: implicit declaration of function
>> 'rt_mutex_futex_unlock' [-Werror=implicit-function-declaration]
rt_mutex_futex_unlock(&rnp->boost_mtx);
^~~~~~~~~~~~~~~~~~~~~
cc1: some warnings being treated as errors
vim +/rt_mutex_futex_unlock +533 kernel/rcu/tree_plugin.h
408
409 /*
410 * Handle special cases during rcu_read_unlock(), such as needing to
411 * notify RCU core processing or task having blocked during the RCU
412 * read-side critical section.
413 */
414 void rcu_read_unlock_special(struct task_struct *t)
415 {
416 bool empty_exp;
417 bool empty_norm;
418 bool empty_exp_now;
419 unsigned long flags;
420 struct list_head *np;
421 bool drop_boost_mutex = false;
422 struct rcu_data *rdp;
423 struct rcu_node *rnp;
424 union rcu_special special;
425
426 /* NMI handlers cannot block and cannot safely manipulate
state. */
427 if (in_nmi())
428 return;
429
430 local_irq_save(flags);
431
432 /*
433 * If RCU core is waiting for this CPU to exit its critical
section,
434 * report the fact that it has exited. Because irqs are
disabled,
435 * t->rcu_read_unlock_special cannot change.
436 */
437 special = t->rcu_read_unlock_special;
438 if (special.b.need_qs) {
439 rcu_preempt_qs();
440 t->rcu_read_unlock_special.b.need_qs = false;
441 if (!t->rcu_read_unlock_special.s) {
442 local_irq_restore(flags);
443 return;
444 }
445 }
446
447 /*
448 * Respond to a request for an expedited grace period, but only
if
449 * we were not preempted, meaning that we were running on the
same
450 * CPU throughout. If we were preempted, the exp_need_qs flag
451 * would have been cleared at the time of the first preemption,
452 * and the quiescent state would be reported when we were
dequeued.
453 */
454 if (special.b.exp_need_qs) {
455 WARN_ON_ONCE(special.b.blocked);
456 t->rcu_read_unlock_special.b.exp_need_qs = false;
457 rdp = this_cpu_ptr(rcu_state_p->rda);
458 rcu_report_exp_rdp(rcu_state_p, rdp, true);
459 if (!t->rcu_read_unlock_special.s) {
460 local_irq_restore(flags);
461 return;
462 }
463 }
464
465 /* Hardware IRQ handlers cannot block, complain if they get
here. */
466 if (in_irq() || in_serving_softirq()) {
467 lockdep_rcu_suspicious(__FILE__, __LINE__,
468 "rcu_read_unlock() from irq or
softirq with blocking in critical section!!!\n");
469 pr_alert("->rcu_read_unlock_special: %#x (b: %d, enq:
%d nq: %d)\n",
470 t->rcu_read_unlock_special.s,
471 t->rcu_read_unlock_special.b.blocked,
472 t->rcu_read_unlock_special.b.exp_need_qs,
473 t->rcu_read_unlock_special.b.need_qs);
474 local_irq_restore(flags);
475 return;
476 }
477
478 /* Clean up if blocked during RCU read-side critical section. */
479 if (special.b.blocked) {
480 t->rcu_read_unlock_special.b.blocked = false;
481
482 /*
483 * Remove this task from the list it blocked on. The
task
484 * now remains queued on the rcu_node corresponding to
the
485 * CPU it first blocked on, so there is no longer any
need
486 * to loop. Retain a WARN_ON_ONCE() out of sheer
paranoia.
487 */
488 rnp = t->rcu_blocked_node;
489 raw_spin_lock_rcu_node(rnp); /* irqs already disabled.
*/
490 WARN_ON_ONCE(rnp != t->rcu_blocked_node);
491 WARN_ON_ONCE(rnp->level != rcu_num_lvls - 1);
492 empty_norm = !rcu_preempt_blocked_readers_cgp(rnp);
493 empty_exp = sync_rcu_preempt_exp_done(rnp);
494 smp_mb(); /* ensure expedited fastpath sees end of RCU
c-s. */
495 np = rcu_next_node_entry(t, rnp);
496 list_del_init(&t->rcu_node_entry);
497 t->rcu_blocked_node = NULL;
498 trace_rcu_unlock_preempted_task(TPS("rcu_preempt"),
499 rnp->gpnum, t->pid);
500 if (&t->rcu_node_entry == rnp->gp_tasks)
501 rnp->gp_tasks = np;
502 if (&t->rcu_node_entry == rnp->exp_tasks)
503 rnp->exp_tasks = np;
504 if (IS_ENABLED(CONFIG_RCU_BOOST)) {
505 /* Snapshot ->boost_mtx ownership w/rnp->lock
held. */
506 drop_boost_mutex =
rt_mutex_owner(&rnp->boost_mtx) == t;
507 if (&t->rcu_node_entry == rnp->boost_tasks)
508 rnp->boost_tasks = np;
509 }
510
511 /*
512 * If this was the last task on the current list, and if
513 * we aren't waiting on any CPUs, report the quiescent
state.
514 * Note that rcu_report_unblock_qs_rnp() releases
rnp->lock,
515 * so we must take a snapshot of the expedited state.
516 */
517 empty_exp_now = sync_rcu_preempt_exp_done(rnp);
518 if (!empty_norm &&
!rcu_preempt_blocked_readers_cgp(rnp)) {
519
trace_rcu_quiescent_state_report(TPS("preempt_rcu"),
520 rnp->gpnum,
521 0, rnp->qsmask,
522 rnp->level,
523 rnp->grplo,
524 rnp->grphi,
525
!!rnp->gp_tasks);
526 rcu_report_unblock_qs_rnp(rcu_state_p, rnp,
flags);
527 } else {
528 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
529 }
530
531 /* Unboost if we were boosted. */
532 if (IS_ENABLED(CONFIG_RCU_BOOST) && drop_boost_mutex)
> 533 rt_mutex_futex_unlock(&rnp->boost_mtx);
534
535 /*
536 * If this was the last task on the expedited lists,
537 * then we need to report up the rcu_node hierarchy.
538 */
539 if (!empty_exp && empty_exp_now)
540 rcu_report_exp_rnp(rcu_state_p, rnp, true);
541 } else {
542 local_irq_restore(flags);
543 }
544 }
545
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