From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
rostedt@goodmis.org, "Paul E. McKenney" <paulmck@kernel.org>,
Neeraj Upadhyay <quic_neeraju@quicinc.com>,
Boqun Feng <boqun.feng@gmail.com>,
Frederic Weisbecker <frederic@kernel.org>
Subject: [PATCH rcu 05/10] rcu: Document reason for rcu_all_qs() call to preempt_disable()
Date: Wed, 31 Aug 2022 11:08:00 -0700 [thread overview]
Message-ID: <20220831180805.2693546-5-paulmck@kernel.org> (raw)
In-Reply-To: <20220831180759.GA2693289@paulmck-ThinkPad-P17-Gen-1>
Given that rcu_all_qs() is in non-preemptible kernels, why on earth should
it invoke preempt_disable()? This commit adds the reason, which is to
work nicely with debugging enabled in CONFIG_PREEMPT_COUNT=y kernels.
Reported-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Reported-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tree_plugin.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 4152816dd29f6..c46b3c74dad1f 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -870,7 +870,7 @@ void rcu_all_qs(void)
if (!raw_cpu_read(rcu_data.rcu_urgent_qs))
return;
- preempt_disable();
+ preempt_disable(); // For CONFIG_PREEMPT_COUNT=y kernels
/* Load rcu_urgent_qs before other flags. */
if (!smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) {
preempt_enable();
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2022-08-31 18:08 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-31 18:07 [PATCH rcu 0/7] Miscellaneous fixes for v6.1 Paul E. McKenney
2022-08-31 18:07 ` [PATCH rcu 01/10] rcu: Fix rcu_read_unlock_strict() strict QS reporting Paul E. McKenney
2022-08-31 18:07 ` [PATCH rcu 02/10] rcu: Update rcu_preempt_deferred_qs() comments for !PREEMPT kernels Paul E. McKenney
2022-08-31 18:07 ` [PATCH rcu 03/10] rcu: Add QS check in rcu_exp_handler() for non-preemptible kernels Paul E. McKenney
2022-09-07 12:10 ` Frederic Weisbecker
2022-09-07 14:57 ` Paul E. McKenney
2022-09-07 15:14 ` Frederic Weisbecker
2022-08-31 18:07 ` [PATCH rcu 04/10] rcu: Make tiny RCU support leak callbacks for debug-object errors Paul E. McKenney
2022-08-31 18:08 ` Paul E. McKenney [this message]
2022-08-31 18:08 ` [PATCH rcu 06/10] rcu: Update rcu_access_pointer() header for rcu_dereference_protected() Paul E. McKenney
2022-08-31 18:08 ` [PATCH rcu 07/10] sched/debug: Try trigger_single_cpu_backtrace(cpu) in dump_cpu_task() Paul E. McKenney
2022-08-31 18:08 ` [PATCH rcu 08/10] sched/debug: Show the registers of 'current' " Paul E. McKenney
2022-08-31 18:08 ` [PATCH rcu 09/10] rcu: Avoid triggering strict-GP irq-work when RCU is idle Paul E. McKenney
2022-08-31 18:08 ` [PATCH rcu 10/10] rcu: Exclude outgoing CPU when it is the last to leave Paul E. McKenney
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