From: Jiri Slaby <jirislaby@gmail.com>
To: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Greg KH <gregkh@suse.de>,
"'devel@driverdev.osuosl.org'" <devel@driverdev.osuosl.org>,
"'virtualization@lists.osdl.org'" <virtualization@lists.osdl.org>,
"'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/1] staging: hv: Fix race condition on IC channel initialization (modified)
Date: Thu, 27 May 2010 08:16:55 +0200 [thread overview]
Message-ID: <4BFE0E57.7050306@gmail.com> (raw)
In-Reply-To: <1FB5E1D5CA062146B38059374562DF7266B8C72B@TK5EX14MBXC128.redmond.corp.microsoft.com>
On 05/26/2010 11:25 PM, Haiyang Zhang wrote:
>> From: Greg KH [mailto:gregkh@suse.de]
>>> + VmbusChannelOpen(newChannel, 2 * PAGE_SIZE,
>>> + 2 * PAGE_SIZE, NULL, 0,
>>> + hv_cb_utils[cnt].callback,
>>> + newChannel) == 0) {
>>> + hv_cb_utils[cnt].channel = newChannel;
>>> + mb();
>>
>> What is the mb() call for? Why is it necessary? (hint, if you need it,
>> something else is really wrong...)
>
> It ensures the channel assignment happens before the wakeup call:
> osd_WaitEventSet(ic_channel_ready), if the compiler optimization re-arrange
> the execution order.
wake_up() is a barrier, you don't need the mb() there.
BTW osd_WaitEventSet et al. can be easily converted to completion.
--
js
next prev parent reply other threads:[~2010-05-27 6:16 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-26 16:54 [PATCH 1/1] staging: hv: Fix race condition on IC channel initialization (modified) Haiyang Zhang
2010-05-26 20:51 ` Greg KH
2010-05-26 21:25 ` Haiyang Zhang
2010-05-26 21:48 ` Greg KH
2010-05-26 22:03 ` Hank Janssen
2010-05-26 22:03 ` Hank Janssen
2010-05-26 22:23 ` Haiyang Zhang
2010-05-26 22:30 ` Greg KH
2010-05-26 22:30 ` Greg KH
2010-05-26 22:52 ` Haiyang Zhang
2010-05-27 23:22 ` Greg KH
2010-05-27 6:16 ` Jiri Slaby [this message]
-- strict thread matches above, loose matches on Subject: below --
2010-05-26 16:54 Haiyang Zhang
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