From: xinhui <xinhui.pan@linux.vnet.ibm.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
waiman.long@hp.com, peterz@infradead.org
Subject: Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian
Date: Thu, 02 Jun 2016 19:01:17 +0800 [thread overview]
Message-ID: <575011FD.4070109@linux.vnet.ibm.com> (raw)
In-Reply-To: <4399273.0kije2Qdx5@wuerfel>
On 2016年06月02日 18:44, Arnd Bergmann wrote:
> On Thursday, June 2, 2016 6:09:08 PM CEST Pan Xinhui wrote:
>> diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
>> index 54a8e65..eadd7a3 100644
>> --- a/include/asm-generic/qrwlock.h
>> +++ b/include/asm-generic/qrwlock.h
>> @@ -139,7 +139,7 @@ static inline void queued_read_unlock(struct qrwlock *lock)
>> */
>> static inline void queued_write_unlock(struct qrwlock *lock)
>> {
>> - smp_store_release((u8 *)&lock->cnts, 0);
>> + (void)atomic_sub_return_release(_QW_LOCKED, &lock->cnts);
>> }
>
> Isn't this more expensive than the existing version?
>
yes, a little more expensive than the existing version
But does this is generic code, I am not sure how it will impact the performance on other archs.
If you like
we calculate the correct address to set to NULL
say,
static inline void queued_write_unlock(struct qrwlock *lock)
{
u8 *wl = lock;
#ifdef __BIG_ENDIAN
wl += 3;
#endif
smp_store_release(wl, 0);
}
> Arnd
>
next prev parent reply other threads:[~2016-06-02 11:02 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-02 10:09 [PATCH] locking/qrwlock: fix write unlock issue in big endian Pan Xinhui
2016-06-02 10:44 ` Arnd Bergmann
2016-06-02 11:01 ` xinhui [this message]
2016-06-02 11:15 ` Peter Zijlstra
2016-06-03 7:20 ` xinhui
2016-06-02 11:02 ` Peter Zijlstra
2016-06-03 7:17 ` xinhui
[not found] ` <201606030718.u537FQg0009963@mx0a-001b2d01.pphosted.com>
2016-06-03 20:57 ` Waiman Long
2016-06-06 3:15 ` xinhui
2016-06-08 9:22 ` Will Deacon
2016-06-14 6:11 ` xinhui
2016-06-14 10:40 ` Will Deacon
2016-06-15 3:47 ` xinhui
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