Commit 09554009 authored Sep 19, 2019 by Mathieu Desnoyers Committed by Ingo Molnar Sep 25, 2019

sched/membarrier: Remove redundant check



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

No change in functionality intended.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190919173705.2181-3-mathieu.desnoyers@efficios.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent fc0d7738

kernel/sched/membarrier.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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.