From: Andi Kleen <andi@firstfloor.org>
To: Alex Shi <alex.shi@intel.com>
Cc: Peter Hurley <peter@hurleysoftware.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Michel Lespinasse <walken@google.com>,
Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Andi Kleen <andi@firstfloor.org>,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
Matthew R Wilcox <matthew.r.wilcox@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Rik van Riel <riel@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH 1/2] rwsem: check the lock before cpmxchg in down_write_trylock and rwsem_do_wake
Date: Sun, 23 Jun 2013 07:10:18 +0200 [thread overview]
Message-ID: <20130623051018.GS6123@two.firstfloor.org> (raw)
In-Reply-To: <51C64C5D.5090400@intel.com>
> >> diff --git a/include/asm-generic/rwsem.h b/include/asm-generic/rwsem.h
> >> index bb1e2cd..052d973 100644
> >> --- a/include/asm-generic/rwsem.h
> >> +++ b/include/asm-generic/rwsem.h
> >> @@ -70,11 +70,11 @@ static inline void __down_write(struct
> >> rw_semaphore *sem)
> >>
> >> static inline int __down_write_trylock(struct rw_semaphore *sem)
> >> {
> >> - long tmp;
> >> + if (unlikely(&sem->count != RWSEM_UNLOCKED_VALUE))
> > ^^^^^^^^^^^
> >
> > This is probably not what you want.
> >
>
> this function logical is quite simple. check the sem->count before
> cmpxchg is no harm this logical.
>
> So could you like to tell us what should we want?
You are comparing the address, not the value. Remove the &
This was a nop too.
-Andi
--
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next prev parent reply other threads:[~2013-06-23 5:10 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1371855277.git.tim.c.chen@linux.intel.com>
2013-06-21 23:51 ` [PATCH 1/2] rwsem: check the lock before cpmxchg in down_write_trylock and rwsem_do_wake Tim Chen
2013-06-22 0:10 ` Alex Shi
2013-06-22 0:15 ` Davidlohr Bueso
2013-06-24 16:34 ` Tim Chen
2013-06-22 7:21 ` Peter Hurley
2013-06-23 1:16 ` Alex Shi
2013-06-23 5:10 ` Andi Kleen [this message]
2013-06-23 11:52 ` Alex Shi
2013-06-21 23:51 ` [PATCH 2/2] rwsem: do optimistic spinning for writer lock acquisition Tim Chen
2013-06-22 0:00 ` Davidlohr Bueso
2013-06-22 7:57 ` Peter Hurley
2013-06-23 20:03 ` Davidlohr Bueso
2013-06-24 17:11 ` Tim Chen
2013-06-24 18:49 ` Peter Hurley
2013-06-24 19:13 ` Tim Chen
2013-06-24 20:32 ` Peter Hurley
2013-06-24 20:17 ` Tim Chen
2013-06-24 20:48 ` Peter Hurley
2013-06-24 21:30 ` Tim Chen
2013-06-25 7:37 ` Peter Zijlstra
2013-06-25 16:00 ` Tim Chen
2013-06-24 21:58 ` Tim Chen
2013-06-24 22:08 ` Peter Hurley
2013-06-24 8:46 ` Peter Zijlstra
2013-06-24 16:36 ` Tim Chen
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