Re: [Qemu-devel] [PATCH 1.1] coroutine: Avoid ucontext usage on i386 Linux host

[Anthony Liguori]

On 05/09/2012 02:57 PM, Jan Kiszka wrote:
> On 2012-05-09 16:48, Anthony Liguori wrote:
> > On 05/09/2012 02:34 PM, Jan Kiszka wrote:
> > > > Can't we resort to the SIGUSR1 workaround for the time being, while
> > > > no RT signals are in actual use, and just have the time to let the
> > > > kernel side to fix the things up before some actual RTsig user will
> > > > emerge in qemu?  I think it is a bit more conservative approach,
> > > > especially having in mind the minority of users this issue affects
> > > > (only 32/64 mixed environment).  I'd favor for this variant, and
> > > > it looks like I'm the "main" 32/64bit user of qemu in this world :)
> > >
> > > Most conservative is definitely this patch, not switching to SIGUSR1,
> > > hoping that no other RT signal user shows up until current kernel are no
> > > longer in use.
> >
> > Sorry, how is using a totally different code path more conservative than using a
> > different signal number?
>
> If the gthread version is not safe to use, why do we fall back to it?

It's safe, but it's significantly slower.

Regards,

Anthony Liguori