linux-kernel - [PATCH] mm/slub: use unchecked percpu access within preemptible sections

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Date:	Tue, 20 Jan 2015 23:31:43 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	linux-kernel@...r.kernel.org
Cc:	iamjoonsoo.kim@....com, cl@...ux.com, brouer@...hat.com,
	akpm@...ux-foundation.org, Sasha Levin <sasha.levin@...cle.com>
Subject: [PATCH] mm/slub: use unchecked percpu access within preemptible sections

Commit "mm/slub: optimize alloc/free fastpath by removing preemption on/off"
has added access to percpu memory while the code is preemptible.

While those accesses are okay, this creates a huge amount of warnings from
the code that checks for that.

Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
---
 mm/slub.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 907fabe..9b72b9c 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2431,8 +2431,8 @@ redo:
 	 * to check if it is matched or not.
 	 */
 	do {
-		tid = this_cpu_read(s->cpu_slab->tid);
-		c = this_cpu_ptr(s->cpu_slab);
+		tid = raw_cpu_read(s->cpu_slab->tid);
+		c = raw_cpu_ptr(s->cpu_slab);
 	} while (IS_ENABLED(CONFIG_PREEMPT) && unlikely(tid != c->tid));
 
 	/*
@@ -2700,8 +2700,8 @@ redo:
 	 * during the cmpxchg then the free will succedd.
 	 */
 	do {
-		tid = this_cpu_read(s->cpu_slab->tid);
-		c = this_cpu_ptr(s->cpu_slab);
+		tid = raw_cpu_read(s->cpu_slab->tid);
+		c = raw_cpu_ptr(s->cpu_slab);
 	} while (IS_ENABLED(CONFIG_PREEMPT) && unlikely(tid != c->tid));
 
 	/* Same with comment on barrier() in slab_alloc_node() */
-- 
1.7.10.4

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