* [PATCH] Fix rq->lock vs logbuf_lock unlock race
@ 2013-02-18 12:53 Bu, Yitian
2013-02-18 14:17 ` [tip:core/printk] printk: Fix rq-> lock vs logbuf_lock unlock lock inversion tip-bot for Bu, Yitian
2013-02-20 8:45 ` [PATCH] Fix rq->lock vs logbuf_lock unlock race Peter Zijlstra
0 siblings, 2 replies; 6+ messages in thread
From: Bu, Yitian @ 2013-02-18 12:53 UTC (permalink / raw)
To: tglx, a.p.zijlstra; +Cc: linux-kernel, mingo
This patch is for kernel V3.7.9
>From 8796f4a2175a323aaa49ea8dd0fe68678dd5dccd Mon Sep 17 00:00:00 2001
From: ybu <ybu@qti.qualcomm.com>
Date: Mon, 18 Feb 2013 19:52:01 +0800
Subject: [PATCH] Fix rq->lock vs logbuf_lock unlock race
fix up the fallout from commit 07354eb1a74d1 ("locking printk:
Annotate logbuf_lock as raw")
Release console_sem after unlocking the logbuf_lock avoids some lock
inversion troubles between logbuf_lock and rq->lock.
Change-Id: I782c1d16e0e82bd156699f0f205f19781c4819e0
Signed-off-by: ybu <ybu@qti.qualcomm.com>
---
kernel/printk.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/printk.c b/kernel/printk.c
index f8e0b5a..3a49454 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1356,9 +1356,9 @@ static int console_trylock_for_printk(unsigned int cpu)
}
}
logbuf_cpu = UINT_MAX;
+ raw_spin_unlock(&logbuf_lock);
if (wake)
up(&console_sem);
- raw_spin_unlock(&logbuf_lock);
return retval;
}
--
1.7.9.5
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [tip:core/printk] printk: Fix rq-> lock vs logbuf_lock unlock lock inversion
2013-02-18 12:53 [PATCH] Fix rq->lock vs logbuf_lock unlock race Bu, Yitian
@ 2013-02-18 14:17 ` tip-bot for Bu, Yitian
2013-02-20 8:45 ` [PATCH] Fix rq->lock vs logbuf_lock unlock race Peter Zijlstra
1 sibling, 0 replies; 6+ messages in thread
From: tip-bot for Bu, Yitian @ 2013-02-18 14:17 UTC (permalink / raw)
To: linux-tip-commits; +Cc: linux-kernel, hpa, mingo, a.p.zijlstra, ybu, tglx
Commit-ID: dbda92d16f8655044e082930e4e9d244b87fde77
Gitweb: http://git.kernel.org/tip/dbda92d16f8655044e082930e4e9d244b87fde77
Author: Bu, Yitian <ybu@qti.qualcomm.com>
AuthorDate: Mon, 18 Feb 2013 12:53:37 +0000
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 18 Feb 2013 15:05:57 +0100
printk: Fix rq->lock vs logbuf_lock unlock lock inversion
commit 07354eb1a74d1 ("locking printk: Annotate logbuf_lock as raw")
reintroduced a lock inversion problem which was fixed in commit
0b5e1c5255 ("printk: Release console_sem after logbuf_lock"). This
happened probably when fixing up patch rejects.
Restore the ordering and unlock logbuf_lock before releasing
console_sem.
Signed-off-by: ybu <ybu@qti.qualcomm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/E807E903FE6CBE4D95E420FBFCC273B827413C@nasanexd01h.na.qualcomm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/printk.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/printk.c b/kernel/printk.c
index 267ce78..e698e80 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1358,9 +1358,9 @@ static int console_trylock_for_printk(unsigned int cpu)
}
}
logbuf_cpu = UINT_MAX;
+ raw_spin_unlock(&logbuf_lock);
if (wake)
up(&console_sem);
- raw_spin_unlock(&logbuf_lock);
return retval;
}
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] Fix rq->lock vs logbuf_lock unlock race
2013-02-18 12:53 [PATCH] Fix rq->lock vs logbuf_lock unlock race Bu, Yitian
2013-02-18 14:17 ` [tip:core/printk] printk: Fix rq-> lock vs logbuf_lock unlock lock inversion tip-bot for Bu, Yitian
@ 2013-02-20 8:45 ` Peter Zijlstra
2013-02-20 9:38 ` Bu, Yitian
1 sibling, 1 reply; 6+ messages in thread
From: Peter Zijlstra @ 2013-02-20 8:45 UTC (permalink / raw)
To: Bu, Yitian; +Cc: tglx, linux-kernel, mingo
On Mon, 2013-02-18 at 12:53 +0000, Bu, Yitian wrote:
> This patch is for kernel V3.7.9
>
> From 8796f4a2175a323aaa49ea8dd0fe68678dd5dccd Mon Sep 17 00:00:00 2001
> From: ybu <ybu@qti.qualcomm.com>
> Date: Mon, 18 Feb 2013 19:52:01 +0800
> Subject: [PATCH] Fix rq->lock vs logbuf_lock unlock race
>
> fix up the fallout from commit 07354eb1a74d1 ("locking printk:
> Annotate logbuf_lock as raw")
> Release console_sem after unlocking the logbuf_lock avoids some lock
> inversion troubles between logbuf_lock and rq->lock.
Please clarify how and where.. you're not actually supposed to use
printk() while holding rq->lock.
^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: [PATCH] Fix rq->lock vs logbuf_lock unlock race
2013-02-20 8:45 ` [PATCH] Fix rq->lock vs logbuf_lock unlock race Peter Zijlstra
@ 2013-02-20 9:38 ` Bu, Yitian
2013-02-20 10:19 ` Peter Zijlstra
0 siblings, 1 reply; 6+ messages in thread
From: Bu, Yitian @ 2013-02-20 9:38 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: tglx, linux-kernel, mingo
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> -----Original Message-----
> From: Peter Zijlstra [mailto:a.p.zijlstra@chello.nl]
> Sent: Wednesday, February 20, 2013 4:45 PM
> To: Bu, Yitian
> Cc: tglx@linutronix.de; linux-kernel@vger.kernel.org; mingo@kernel.org
> Subject: Re: [PATCH] Fix rq->lock vs logbuf_lock unlock race
>
> On Mon, 2013-02-18 at 12:53 +0000, Bu, Yitian wrote:
> > This patch is for kernel V3.7.9
> >
> > From 8796f4a2175a323aaa49ea8dd0fe68678dd5dccd Mon Sep 17 00:00:00
> 2001
> > From: ybu <ybu@qti.qualcomm.com>
> > Date: Mon, 18 Feb 2013 19:52:01 +0800
> > Subject: [PATCH] Fix rq->lock vs logbuf_lock unlock race
> >
> > fix up the fallout from commit 07354eb1a74d1 ("locking printk:
> > Annotate logbuf_lock as raw")
> > Release console_sem after unlocking the logbuf_lock avoids some lock
> > inversion troubles between logbuf_lock and rq->lock.
>
> Please clarify how and where.. you're not actually supposed to use
> printk() while holding rq->lock.
>
1. the patch 0b5e1c5255e, which is written by you, release console_sem
after logbuf_lock. But the patch 07354eb1a revert one of your change, it
reintroduced a lock inversion problem which was fixed in 0b5e1c5255.
The purpose of my patch is the same as your patch 0b5e1c5255e.
2. from printk comment: "This is printk(). It can be called from any context.
We want it to work. ". I suppose to use printk in any context.
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Fix rq->lock vs logbuf_lock unlock race
2013-02-20 9:38 ` Bu, Yitian
@ 2013-02-20 10:19 ` Peter Zijlstra
2013-02-20 11:24 ` Bu, Yitian
0 siblings, 1 reply; 6+ messages in thread
From: Peter Zijlstra @ 2013-02-20 10:19 UTC (permalink / raw)
To: Bu, Yitian; +Cc: tglx, linux-kernel, mingo
On Wed, 2013-02-20 at 09:38 +0000, Bu, Yitian wrote:
>
> 2. from printk comment: "This is printk(). It can be called from any
> context.
> We want it to work. ". I suppose to use printk in any context.
Unfortunately that's not quite possible, rq->lock is really out of
bounds. At one point I tried 'fixing' this but there's a whole bunch of
nasty that's not going to go away.
I've since forgotten most of the details, but aside from logbuf problems
there's a whole host of issues with the console drivers themselves as
well.
If you really want to do this, use early_printk.
^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: [PATCH] Fix rq->lock vs logbuf_lock unlock race
2013-02-20 10:19 ` Peter Zijlstra
@ 2013-02-20 11:24 ` Bu, Yitian
0 siblings, 0 replies; 6+ messages in thread
From: Bu, Yitian @ 2013-02-20 11:24 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: tglx, linux-kernel, mingo
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> Unfortunately that's not quite possible, rq->lock is really out of bounds. At
> one point I tried 'fixing' this but there's a whole bunch of nasty that's not
> going to go away.
>
> I've since forgotten most of the details, but aside from logbuf problems
> there's a whole host of issues with the console drivers themselves as well.
>
> If you really want to do this, use early_printk.
Hi Peter:
The patch 0b5e1c5255e("printk: Release console_sem after logbuf_lock" )
is as below:
console_locked = 0;
- up(&console_sem);
+ wake = 1;
retval = 0;
}
}
printk_cpu = UINT_MAX;
spin_unlock(&logbuf_lock);
+ if (wake)
+ up(&console_sem);
return retval;
the patch 07354eb1a74d1("locking, printk: Annotate logbuf_lock as raw ")
is as below:
printk_cpu = UINT_MAX;
- spin_unlock(&logbuf_lock);
if (wake)
up(&console_sem);
+ raw_spin_unlock(&logbuf_lock);
return retval;
}
Note that the purpose of patch 07354eb1a74d1 is to use raw_spin_unlock
instead of spin_unlock, it is not supposed to change any lock sequences.
What I do is to revert this change to 0b5e1c5255e, and it is nothing to do with
how people use printk. It is just to recover a merge mistake.
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2013-02-20 11:24 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2013-02-18 12:53 [PATCH] Fix rq->lock vs logbuf_lock unlock race Bu, Yitian
2013-02-18 14:17 ` [tip:core/printk] printk: Fix rq-> lock vs logbuf_lock unlock lock inversion tip-bot for Bu, Yitian
2013-02-20 8:45 ` [PATCH] Fix rq->lock vs logbuf_lock unlock race Peter Zijlstra
2013-02-20 9:38 ` Bu, Yitian
2013-02-20 10:19 ` Peter Zijlstra
2013-02-20 11:24 ` Bu, Yitian
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