Re: Thread safety of coroutine-sigaltstack

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Jan 21, 2021 at 04:14:21PM +0100, Paolo Bonzini wrote:
> On 21/01/21 10:27, Max Reitz wrote:
> > 
> > Sure, I can do that.
> > 
> > I agree that there probably are better solutions than to wrap everything
> > in a lock.  OTOH, it looks to me like this lock is the most simple
> > solution.  If Daniel is right[1] and we should drop
> > coroutine-sigaltstack altogether (at some point...), perhaps it is best
> > to go for the most simple solution now.
> > 
> > [1]
> > https://lists.nongnu.org/archive/html/qemu-block/2021-01/msg00808.html
> 
> Yes, between coroutine-ucontext and the upcoming coroutine-asm[1] (which I
> have shelved because it was mostly a requirement for x86 CET; but it will
> come back some day), sooner or later there will be no reason to keep
> coroutine-sigaltstack.  Porting coroutine-asm to a new architecture is easy,
> I even managed to do it for s390. ;)

FWIW The libucontext impl is all ASM based and has coverage for all the
arches we care about:

   https://github.com/kaniini/libucontext

so doesn't seem like there's a need for  coroutine-asm if we can rely
on libucontext for portability where neede.

Regards,
Daniel
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