From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Dave Jones <davej@redhat.com>,
bhutchings@solarflare.com,
Konstantin Khlebnikov <khlebnikov@openvz.org>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Hugh Dickins <hughd@google.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in numa_maps
Date: Tue, 16 Oct 2012 21:53:02 -0400 [thread overview]
Message-ID: <CAHGf_=pVx=7nCZ1+e2M+bKH=SUGJa585+QxFbNboaq7_vy4MVw@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1210161847060.20503@chino.kir.corp.google.com>
On Tue, Oct 16, 2012 at 9:49 PM, David Rientjes <rientjes@google.com> wrote:
> On Tue, 16 Oct 2012, KOSAKI Motohiro wrote:
>
>> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>> > index 0b78fb9..d04a8a5 100644
>> > --- a/mm/mempolicy.c
>> > +++ b/mm/mempolicy.c
>> > @@ -1536,9 +1536,8 @@ asmlinkage long compat_sys_mbind(compat_ulong_t start, compat_ulong_t len,
>> > *
>> > * Returns effective policy for a VMA at specified address.
>> > * Falls back to @task or system default policy, as necessary.
>> > - * Current or other task's task mempolicy and non-shared vma policies
>> > - * are protected by the task's mmap_sem, which must be held for read by
>> > - * the caller.
>> > + * Current or other task's task mempolicy and non-shared vma policies must be
>> > + * protected by task_lock(task) by the caller.
>>
>> This is not correct. mmap_sem is needed for protecting vma. task_lock()
>> is needed to close vs exit race only when task != current. In other word,
>> caller must held both mmap_sem and task_lock if task != current.
>
> The comment is specifically addressing non-shared vma policies, you do not
> need to hold mmap_sem to access another thread's mempolicy.
I didn't say old comment is true. I just only your new comment also false.
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next prev parent reply other threads:[~2012-10-17 1:53 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-08 15:09 mpol_to_str revisited Dave Jones
2012-10-08 15:15 ` Dave Jones
2012-10-08 20:46 ` David Rientjes
2012-10-08 20:35 ` David Rientjes
2012-10-08 20:52 ` Dave Jones
2012-10-16 0:48 ` David Rientjes
2012-10-09 0:33 ` Ben Hutchings
2012-10-16 2:34 ` KOSAKI Motohiro
2012-10-16 3:58 ` David Rientjes
2012-10-16 5:10 ` KOSAKI Motohiro
2012-10-16 6:10 ` David Rientjes
2012-10-16 23:39 ` KOSAKI Motohiro
2012-10-17 0:12 ` David Rientjes
2012-10-17 0:31 ` [patch for-3.7] mm, mempolicy: fix printing stack contents in numa_maps David Rientjes
2012-10-17 1:38 ` KOSAKI Motohiro
2012-10-17 1:49 ` David Rientjes
2012-10-17 1:53 ` KOSAKI Motohiro [this message]
2012-10-17 4:05 ` Dave Jones
2012-10-17 5:24 ` David Rientjes
2012-10-17 5:42 ` Kamezawa Hiroyuki
2012-10-17 8:49 ` KOSAKI Motohiro
2012-10-17 19:50 ` David Rientjes
2012-10-17 21:05 ` KOSAKI Motohiro
2012-10-17 21:27 ` David Rientjes
2012-10-17 18:14 ` Dave Jones
2012-10-17 19:21 ` David Rientjes
2012-10-17 19:32 ` Dave Jones
2012-10-17 19:38 ` David Rientjes
2012-10-17 19:45 ` Dave Jones
2012-10-17 20:28 ` [patch for-3.7] mm, mempolicy: avoid taking mutex inside spinlock when reading numa_maps David Rientjes
2012-10-17 21:31 ` [patch for-3.7 v2] " David Rientjes
2012-10-18 4:06 ` Kamezawa Hiroyuki
2012-10-18 4:14 ` Linus Torvalds
2012-10-18 4:41 ` Kamezawa Hiroyuki
2012-10-18 4:34 ` Kamezawa Hiroyuki
2012-10-18 20:03 ` David Rientjes
2012-10-19 8:35 ` [patch for-3.7 v3] mm, mempolicy: hold task->mempolicy refcount while " Kamezawa Hiroyuki
2012-10-19 9:28 ` David Rientjes
2012-10-22 2:47 ` Kamezawa Hiroyuki
2012-10-22 20:55 ` Andrew Morton
2012-10-22 20:56 ` David Rientjes
2012-10-19 19:15 ` KOSAKI Motohiro
2012-10-19 6:51 ` [patch for-3.7 v2] mm, mempolicy: avoid taking mutex inside spinlock when " KOSAKI Motohiro
2012-10-18 4:35 ` David Rientjes
2012-10-24 23:30 ` [patch for-3.7] mm, mempolicy: fix printing stack contents in numa_maps Sasha Levin
2012-10-24 23:34 ` David Rientjes
2012-10-24 23:37 ` Sasha Levin
2012-10-25 0:08 ` David Rientjes
2012-10-25 0:54 ` KOSAKI Motohiro
2012-10-25 1:15 ` David Rientjes
2012-10-25 12:19 ` Peter Zijlstra
2012-10-25 14:39 ` Peter Zijlstra
2012-10-25 17:23 ` Sasha Levin
2012-10-25 20:22 ` David Rientjes
2012-10-25 23:09 ` Linus Torvalds
2012-10-26 8:48 ` Peter Zijlstra
2012-10-31 18:29 ` Sasha Levin
2012-11-21 0:59 ` Sasha Levin
2012-10-17 1:33 ` mpol_to_str revisited KOSAKI Motohiro
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