The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     09554009c0cad4cb2223dd943c813c9257c6883a
Gitweb:        
https://git.kernel.org/tip/09554009c0cad4cb2223dd943c813c9257c6883a
Author:        Mathieu Desnoyers <[email protected]>
AuthorDate:    Thu, 19 Sep 2019 13:37:00 -04:00
Committer:     Ingo Molnar <[email protected]>
CommitterDate: Wed, 25 Sep 2019 17:42:30 +02:00

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 <[email protected]>
Signed-off-by: Mathieu Desnoyers <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Eric W. Biederman <[email protected]>
Cc: Kirill Tkhai <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Russell King - ARM Linux admin <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: 
https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
 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 d48b95f..7ccbd0e 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.

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