linux-kernel - Re: [RFC][PATCH 1/8] epoll: remove epmutex from ep_free() & eventpoll_release

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Date:   Mon, 30 Oct 2017 15:09:59 +0800
From:   Hou Tao <houtao1@...wei.com>
To:     Davidlohr Bueso <dave@...olabs.net>
CC:     <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <viro@...iv.linux.org.uk>, <jbaron@...mai.com>, <oleg@...hat.com>,
        <koct9i@...il.com>
Subject: Re: [RFC][PATCH 1/8] epoll: remove epmutex from ep_free() &
 eventpoll_release_file()

Hi,

On 2017/10/28 21:58, Davidlohr Bueso wrote:
> On Sat, 28 Oct 2017, Hou Tao wrote:
> 
>> Remove the global epmutex from ep_free() and eventpoll_release_file().
>> In the later patches, we will add locks with a smaller granularity
>> to serve the same purposes of epmutex.
>>
>> Signed-off-by: Hou Tao <houtao1@...wei.com>
>> ---
>> fs/eventpoll.c | 4 ----
>> 1 file changed, 4 deletions(-)
>>
>> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
>> index 2fabd19..26ab0c5 100644
>> --- a/fs/eventpoll.c
>> +++ b/fs/eventpoll.c
>> @@ -835,7 +835,6 @@ static void ep_free(struct eventpoll *ep)
>>      * anymore. The only hit might come from eventpoll_release_file() but
>>      * holding "epmutex" is sufficient here.
>>      */
> ^^
> What about this comment (and the equivalent one in eventpoll_release_file()?
> 
>> -    mutex_lock(&epmutex);
> 
Thanks for your reminder. I will fix the related comments in a v1 patchset.

> ...even if you fix it in a later patch, this patch breaks bisection. Now
> we just race between ep_free() and eventpoll_release_file(). This patch
> should be folded in, no?
Yes, the patchset should be squashed into one patch, however it will be
difficult to explain the purpose of these modifications, so I break them
into little pieces, and hoped that these little patches can explain the
reason why the modification is needed in a cleaner way. It also will
be fixed in v1 patch.

Regards,

Tao

> Thanks,
> Davidlohr
> 
> .
>