1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
|
From patchwork Wed Sep 14 19:43:15 2011
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: powerpc: Fix deadlock in icswx code
Date: Wed, 14 Sep 2011 09:43:15 -0000
From: Anton Blanchard <anton@samba.org>
X-Patchwork-Id: 114701
Message-Id: <20110915054315.5e5ae062@kryten>
To: benh@kernel.crashing.org, paulus@samba.org
Cc: linuxppc-dev@lists.ozlabs.org
The icswx code introduced an A-B B-A deadlock:
CPU0 CPU1
---- ----
lock(&anon_vma->mutex);
lock(&mm->mmap_sem);
lock(&anon_vma->mutex);
lock(&mm->mmap_sem);
Instead of using the mmap_sem to keep mm_users constant, take the
page table spinlock.
Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: <stable@kernel.org>
---
diff --git a/arch/powerpc/mm/mmu_context_hash64.c b/arch/powerpc/mm/mmu_context_hash64.c
index 3bafc3d..4ff587e 100644
--- a/arch/powerpc/mm/mmu_context_hash64.c
+++ b/arch/powerpc/mm/mmu_context_hash64.c
@@ -136,8 +136,8 @@ int use_cop(unsigned long acop, struct mm_struct *mm)
if (!mm || !acop)
return -EINVAL;
- /* We need to make sure mm_users doesn't change */
- down_read(&mm->mmap_sem);
+ /* The page_table_lock ensures mm_users won't change under us */
+ spin_lock(&mm->page_table_lock);
spin_lock(mm->context.cop_lockp);
if (mm->context.cop_pid == COP_PID_NONE) {
@@ -164,7 +164,7 @@ int use_cop(unsigned long acop, struct mm_struct *mm)
out:
spin_unlock(mm->context.cop_lockp);
- up_read(&mm->mmap_sem);
+ spin_unlock(&mm->page_table_lock);
return ret;
}
@@ -185,8 +185,8 @@ void drop_cop(unsigned long acop, struct mm_struct *mm)
if (WARN_ON_ONCE(!mm))
return;
- /* We need to make sure mm_users doesn't change */
- down_read(&mm->mmap_sem);
+ /* The page_table_lock ensures mm_users won't change under us */
+ spin_lock(&mm->page_table_lock);
spin_lock(mm->context.cop_lockp);
mm->context.acop &= ~acop;
@@ -213,7 +213,7 @@ void drop_cop(unsigned long acop, struct mm_struct *mm)
}
spin_unlock(mm->context.cop_lockp);
- up_read(&mm->mmap_sem);
+ spin_unlock(&mm->page_table_lock);
}
EXPORT_SYMBOL_GPL(drop_cop);
|
