On 9 May 2012 11:11, Kevin Wolf <kw...@redhat.com> wrote: > Am 08.05.2012 21:35, schrieb Jan Kiszka: >> I hunted down a fairly subtle corruption of the VCPU thread signal mask >> in KVM mode when using the ucontext version of coroutines: >> >> coroutine_new calls getcontext, makecontext, swapcontext. Those >> functions get/set also the signal mask of the caller. Unfortunately, >> they only use the sigprocmask syscall on i386, not the rt_sigprocmask >> version. So they do not properly save/restore the blocked RT signals, >> namely our SIG_IPI - it becomes unblocke this way. > > If other coroutine backends work (sigaltstack?), we could try to detect > the situation in configure and set the right default. Not sure what the > condition is, glibc + i386?
I don't think you can do a compile-time test for this short of just disabling use of the ucontext code on all i386/Linux platforms. I think it's becoming increasingly obvious that the setcontext/getcontext code path is not very well used and prone to nasty libc bugs. Trying to implement coroutines in C is just a really bad idea and I think we should be trying to reduce our use of them if we possibly can, presumably by switching to actually using threads where we really need the parallelism. -- PMM
