[PATCH] sched/numa: kill the wrong/dead TASK_DEAD check in task_numa_fault()

[PATCH] sched/numa: kill the wrong/dead TASK_DEAD check in task_numa_fault()

[Oleg Nesterov]

current->state == TASK_DEAD means that the task is doing its last
schedule(), page fault is obviously impossible at this stage.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/sched/fair.c |    4 ----
 1 files changed, 0 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 82088b2..0090e8c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1804,10 +1804,6 @@ void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
 	if (!p->mm)
 		return;
 
-	/* Do not worry about placement if exiting */
-	if (p->state == TASK_DEAD)
-		return;
-
 	/* Allocate buffer to track faults on a per-node basis */
 	if (unlikely(!p->numa_faults_memory)) {
 		int size = sizeof(*p->numa_faults_memory) *
-- 
1.5.5.1

Re: [PATCH] sched/numa: kill the wrong/dead TASK_DEAD check in task_numa_fault()

[Mel Gorman]

On Sun, Sep 21, 2014 at 09:47:43PM +0200, Oleg Nesterov wrote:
> current->state == TASK_DEAD means that the task is doing its last
> schedule(), page fault is obviously impossible at this stage.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

I was going to complain that the check would protect against a spurious
allocation during fault but a task in this state should not be faulting
any more.

Acked-by: Mel Gorman <mgorman@suse.de>

Thanks.

-- 
Mel Gorman
SUSE Labs

Re: [PATCH] sched/numa: kill the wrong/dead TASK_DEAD check in task_numa_fault()

[Rik van Riel]

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On 09/21/2014 03:47 PM, Oleg Nesterov wrote:
> current->state == TASK_DEAD means that the task is doing its last 
> schedule(), page fault is obviously impossible at this stage.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Rik van Riel <riel@redhat.com>

- -- 
All rights reversed
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[tip:sched/core] sched/numa: Kill the wrong/ dead TASK_DEAD check in task_numa_fault()

[tip-bot for Oleg Nesterov]

Commit-ID:  be34f0f3e6aed6e828a8059247d169d38da128d7
Gitweb:     http://git.kernel.org/tip/be34f0f3e6aed6e828a8059247d169d38da128d7
Author:     Oleg Nesterov <oleg@redhat.com>
AuthorDate: Sun, 21 Sep 2014 21:47:43 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Sep 2014 09:35:05 +0200

sched/numa: Kill the wrong/dead TASK_DEAD check in task_numa_fault()

current->state == TASK_DEAD means that the task is doing its
last schedule(), page fault is obviously impossible at this
stage.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140921194743.GA30114@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/fair.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2a1e6ac..9ee3d4f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1817,10 +1817,6 @@ void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
 	if (!p->mm)
 		return;
 
-	/* Do not worry about placement if exiting */
-	if (p->state == TASK_DEAD)
-		return;
-
 	/* Allocate buffer to track faults on a per-node basis */
 	if (unlikely(!p->numa_faults_memory)) {
 		int size = sizeof(*p->numa_faults_memory) *