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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Peter Zijlstra <peterz@infradead.org>,
	"Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>,
	linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Russell King - ARM Linux admin <linux@armlinux.org.uk>,
	Chris Metcalf <cmetcalf@ezchip.com>,
	Christoph Lameter <cl@linux.com>, Kirill Tkhai <tkhai@yandex.ru>,
	Mike Galbraith <efault@gmx.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: [RFC PATCH 2/4] Cleanup: sched/membarrier: remove redundant check
Date: Thu,  5 Sep 2019 23:12:58 -0400	[thread overview]
Message-ID: <20190906031300.1647-3-mathieu.desnoyers@efficios.com> (raw)
In-Reply-To: <20190906031300.1647-1-mathieu.desnoyers@efficios.com>

Checking that the number of threads is 1 is redundant with checking
mm_users == 1.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/membarrier.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index 5110d91b1b0e..7e0a0d6535f3 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -186,7 +186,7 @@ static int membarrier_register_global_expedited(void)
 	    MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY)
 		return 0;
 	atomic_or(MEMBARRIER_STATE_GLOBAL_EXPEDITED, &mm->membarrier_state);
-	if (atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1) {
+	if (atomic_read(&mm->mm_users) == 1) {
 		/*
 		 * For single mm user, single threaded process, we can
 		 * simply issue a memory barrier after setting
@@ -232,7 +232,7 @@ static int membarrier_register_private_expedited(int flags)
 	if (flags & MEMBARRIER_FLAG_SYNC_CORE)
 		atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE,
 			  &mm->membarrier_state);
-	if (!(atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1)) {
+	if (atomic_read(&mm->mm_users) != 1) {
 		/*
 		 * Ensure all future scheduler executions will observe the
 		 * new thread flag state for this process.
-- 
2.17.1


  parent reply	other threads:[~2019-09-06  3:13 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-06  3:12 [RFC PATCH 0/4] Membarrier fixes/cleanups Mathieu Desnoyers
2019-09-06  3:12 ` [RFC PATCH 1/4] Fix: sched/membarrier: private expedited registration check Mathieu Desnoyers
2019-09-06  3:12 ` Mathieu Desnoyers [this message]
2019-09-06  3:12 ` [RFC PATCH 3/4] Cleanup: sched/membarrier: only sync_core before usermode for same mm Mathieu Desnoyers
2019-09-06  7:41   ` Peter Zijlstra
2019-09-06 13:40     ` Mathieu Desnoyers
2019-09-06  3:13 ` [RFC PATCH 4/4] Fix: sched/membarrier: p->mm->membarrier_state racy load Mathieu Desnoyers
2019-09-06  8:23   ` Peter Zijlstra
2019-09-08 13:49     ` [RFC PATCH 4/4] Fix: sched/membarrier: p->mm->membarrier_state racy load (v2) Mathieu Desnoyers
2019-09-08 16:51       ` Linus Torvalds
2019-09-10  9:48         ` Mathieu Desnoyers
2019-09-12 13:48           ` Will Deacon
2019-09-12 14:24             ` Linus Torvalds
2019-09-12 15:47               ` Will Deacon
2019-09-13 14:22                 ` Mathieu Desnoyers
2019-09-19 16:26                   ` Will Deacon
2019-09-19 17:33                     ` Mathieu Desnoyers
2019-09-09 11:00       ` Oleg Nesterov
2019-09-13 15:20         ` Mathieu Desnoyers
2019-09-13 16:04           ` Oleg Nesterov
2019-09-13 17:07             ` Mathieu Desnoyers

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