lkml.org 
[lkml]   [2019]   [Sep]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip: sched/urgent] sched/membarrier: Skip IPIs when mm->mm_users == 1
The following commit has been merged into the sched/urgent branch of tip:

Commit-ID: c6d68c1c4a4d6611fc0f8145d764226571d737ca
Gitweb: https://git.kernel.org/tip/c6d68c1c4a4d6611fc0f8145d764226571d737ca
Author: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
AuthorDate: Thu, 19 Sep 2019 13:37:04 -04:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 25 Sep 2019 17:42:31 +02:00

sched/membarrier: Skip IPIs when mm->mm_users == 1

If there is only a single mm_user for the mm, the private expedited
membarrier command can skip the IPIs, because only a single thread
is using the mm.

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: Oleg Nesterov <oleg@redhat.com>
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/20190919173705.2181-7-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/membarrier.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index 070cf43..fced54a 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -145,20 +145,21 @@ static int membarrier_private_expedited(int flags)
int cpu;
bool fallback = false;
cpumask_var_t tmpmask;
+ struct mm_struct *mm = current->mm;

if (flags & MEMBARRIER_FLAG_SYNC_CORE) {
if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE))
return -EINVAL;
- if (!(atomic_read(&current->mm->membarrier_state) &
+ if (!(atomic_read(&mm->membarrier_state) &
MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY))
return -EPERM;
} else {
- if (!(atomic_read(&current->mm->membarrier_state) &
+ if (!(atomic_read(&mm->membarrier_state) &
MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY))
return -EPERM;
}

- if (num_online_cpus() == 1)
+ if (atomic_read(&mm->mm_users) == 1 || num_online_cpus() == 1)
return 0;

/*
@@ -194,7 +195,7 @@ static int membarrier_private_expedited(int flags)
continue;
rcu_read_lock();
p = rcu_dereference(cpu_rq(cpu)->curr);
- if (p && p->mm == current->mm) {
+ if (p && p->mm == mm) {
if (!fallback)
__cpumask_set_cpu(cpu, tmpmask);
else
\
 
 \ /
  Last update: 2019-09-27 10:12    [W:0.274 / U:0.280 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site