Re: [RESEND][RFC PATCH v2] waitfd

Casey Dahlin
2009-01-10T21:15:27Z

Scott James Remnant wrote:
> On Wed, 2009-01-07 at 18:19 +0100, Oleg Nesterov wrote:
>
>
>> Please note that unlike other sys_...fd() syscalls, sys_waitfd()
>> doesn't allow to pass O_CLOEXEC. Looks like we need a separate
>> "flags" argument...
>>
>> Also, ioctl(FIONBIO) or fcntl(O_NONBLOCK) have no effect on
>> waitfd, not very good.
>>
>> I'd suggest to remove WNOHANG from waitfd_ctx->ops and treat
>> (->f_flags & O_NONBLOCK) as WNOHANG.
>>
>> (can't resist, ->ops is not the best name ;)
>>
>>
> Definitely agree here, waitfd() doesn't need WNOHANG - we already have
> ONONBLOCK.
>
> That also solves one of the strangest behaves of waitid when you use
> WNOHANG (it returns zero and you have to check whether it changed the
> struct), now you just read() - if no child you get EAGAIN, if a child
> you read a struct.
>
> Scott
>
From the perspective of waitfd, the only difference between WNOHANG and
O_NONBLOCK is which argument you put the flags in. The API should only
support one or the other, but internally they would imply the same thing.

--CJD