Re: [PATCH-RFC 2/2] eventfd: EFD_STATE flag

Avi Kivity
2009-08-04T09:25:10Z

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.

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