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-rw-r--r--kernel/rcuclassic.c30
1 files changed, 29 insertions, 1 deletions
diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index f4ffbd0f306f..d8348792f9f5 100644
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -502,10 +502,38 @@ void rcu_check_callbacks(int cpu, int user)
502 if (user || 502 if (user ||
503 (idle_cpu(cpu) && !in_softirq() && 503 (idle_cpu(cpu) && !in_softirq() &&
504 hardirq_count() <= (1 << HARDIRQ_SHIFT))) { 504 hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
505
506 /*
507 * Get here if this CPU took its interrupt from user
508 * mode or from the idle loop, and if this is not a
509 * nested interrupt. In this case, the CPU is in
510 * a quiescent state, so count it.
511 *
512 * Also do a memory barrier. This is needed to handle
513 * the case where writes from a preempt-disable section
514 * of code get reordered into schedule() by this CPU's
515 * write buffer. The memory barrier makes sure that
516 * the rcu_qsctr_inc() and rcu_bh_qsctr_inc() are see
517 * by other CPUs to happen after any such write.
518 */
519
520 smp_mb(); /* See above block comment. */
505 rcu_qsctr_inc(cpu); 521 rcu_qsctr_inc(cpu);
506 rcu_bh_qsctr_inc(cpu); 522 rcu_bh_qsctr_inc(cpu);
507 } else if (!in_softirq()) 523
524 } else if (!in_softirq()) {
525
526 /*
527 * Get here if this CPU did not take its interrupt from
528 * softirq, in other words, if it is not interrupting
529 * a rcu_bh read-side critical section. This is an _bh
530 * critical section, so count it. The memory barrier
531 * is needed for the same reason as is the above one.
532 */
533
534 smp_mb(); /* See above block comment. */
508 rcu_bh_qsctr_inc(cpu); 535 rcu_bh_qsctr_inc(cpu);
536 }
509 raise_rcu_softirq(); 537 raise_rcu_softirq();
510} 538}
511 539