linux-kernel - Re: [PATCH-RFC 2/2] eventfd: EFD

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Message-ID: <4A77FFB5.4060201@redhat.com>
Date:	Tue, 04 Aug 2009 12:30:29 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	"Michael S. Tsirkin" <mst@...hat.com>, davidel@...ilserver.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH-RFC 2/2] eventfd: EFD_STATE flag

On 08/04/2009 12:23 PM, Gleb Natapov wrote:
> On Tue, Aug 04, 2009 at 12:25:49PM +0300, Avi Kivity wrote:
>    
>> On 08/04/2009 12:17 PM, Gleb Natapov wrote:
>>      
>>>> If a different read comes after the write but after our read, it will
>>>> have transferred the value, resulting in the same situation.
>>>>
>>>> I think reads should never block with a state based mechanism.
>>>>
>>>>
>>>>          
>>> Reader may want to poll for the status change.
>>>
>>>        
>> Without epoll(), it's inherently racy since reads from other processes
>> can clear the status.
>>
>>      
> This is correct for any file descriptor. Multiple readers shouldn't
> simultaneously read from the same files descriptor if they expect to
> make any sense from a result.
>    

I think counting eventfd is an exception, but in general you are right.

-- 
error compiling committee.c: too many arguments to function

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