On Mon, Oct 25, 2021 at 10:18 AM Richard Henderson < [email protected]> wrote:
> On 10/25/21 7:07 AM, Stefan Hajnoczi wrote: > > This is a preview of how we can solve the coroutines TLS problem. > Coroutines > > re-entered from another thread sometimes see stale TLS values. This > happens > > because compilers may cache values across yield points, so a value from > the > > previous thread will be used when the coroutine is re-entered in another > > thread. > > I'm not thrilled by this, but I guess it does work. > > It could be worthwhile to add some inline asm instead for specific hosts > -- one > instruction instead of an out-of-line call. > > > > Serge Guelton developed this technique, see the first patch for details. > I'm > > submitting it for discussion before I go ahead with a full conversion of > the > > source tree. > > > > Todo: > > - Convert all uses of __thread > > - Extend checkpatch.pl to reject code that uses __thread > > Absolutely not. *Perhaps* one or two tls variables which are accessible > by coroutines, > but there are plenty that have absolutely no relation. Especially > everything related to > user-only execution. > I had the same worry. I'd also worry that the hoops that are jumped through for coroutines would somehow conflict with the low-level user-only execution environment. I mean, it should be fine, but I know I'd be cranky if I traced obscure regressions to being forced to use this construct... Warner > r~ > >
