Re: [kvm-devel] [PATCH] Use pipe() to simulate signalfd() (v2)

[Avi K. <av...@qu...>]

Anthony Liguori wrote:
> This patch reworks the IO thread to use signalfd() instead of sigtimedwait().
> This will eliminate the need to use SIGIO everywhere.  In this version of the
> patch, we use signalfd() when it's available.  When it isn't available, we
> instead use a pipe() that is written to in each signal handler.
>
> I've tested Windows and Linux guests with SMP without seeing an obvious
> regressions.
>
>   

Please split the signalfd() emulation into a separate (preparatory) 
patch.  Also, we need to detect signalfd() at run time as well as 
compile time, since qemu may be compiled on a different machine than it 
is run on.

> +/* If we don't have signalfd, we don't mask out the signals we want to receive.
> + * To avoid the signal/select race, we use a pipe() that we write to from the
> + * signal handler.  As a consequence, we save off the signal handler to perform
> + * dispatch.
> + */
>   

We can keep the signals blocked, but run the signalfd emulation in a 
separate thread (where it can dequeue signals using sigwait as an added 
bonus).  This will reduce the differences between the two modes at the 
expense of increased signalfd() emulation complexity, which I think is a 
good tradeoff.

We can move signalfd emulation into a separate file in order to improve 
readability.

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