linux-kernel - [PATCH 01/20] percpu: fix pcpu

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Message-Id: <1248171979-29166-2-git-send-email-tj@kernel.org>
Date:	Tue, 21 Jul 2009 19:26:00 +0900
From:	Tejun Heo <tj@...nel.org>
To:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	mingo@...hat.com, benh@...nel.crashing.org, davem@...emloft.net,
	dhowells@...hat.com, npiggin@...e.de, JBeulich@...ell.com,
	cl@...ux-foundation.org, rusty@...tcorp.com.au, hpa@...or.com,
	tglx@...utronix.de, akpm@...ux-foundation.org, x86@...nel.org,
	andi@...stfloor.org
Cc:	Tejun Heo <tj@...nel.org>
Subject: [PATCH 01/20] percpu: fix pcpu_reclaim() locking

pcpu_reclaim() calls pcpu_depopulate_chunk() which makes use of pages
array and bitmap returned by pcpu_get_pages_and_bitmap() and thus
should be called under pcpu_alloc_mutex.  pcpu_reclaim() released the
mutex before calling depopulate leading to double free and other
strange problems caused by the unexpected concurrent usages of pages
array and bitmap.  Fix it.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 mm/percpu.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index f993dc8..c44a5b2 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1181,12 +1181,13 @@ static void pcpu_reclaim(struct work_struct *work)
 	}
 
 	spin_unlock_irq(&pcpu_lock);
-	mutex_unlock(&pcpu_alloc_mutex);
 
 	list_for_each_entry_safe(chunk, next, &todo, list) {
 		pcpu_depopulate_chunk(chunk, 0, pcpu_unit_size);
 		free_pcpu_chunk(chunk);
 	}
+
+	mutex_unlock(&pcpu_alloc_mutex);
 }
 
 /**
-- 
1.6.0.2

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