On Thu, May 11, 2023 at 8:44 PM Florian Weimer <fwei...@redhat.com> wrote: > Apparently, Hurd does not support async cancellation? Then > __pthread_setcancelstate never has to unwind, so you just turn it into a > non-weak symbol.
It does in theory, htl/pt-cancel.c has a PTHREAD_CANCEL_ASYNCHRONOUS branch that calls into sysdeps/mach/hurd/htl/pt-docancel.c, which manipulates the victim thread's state to make it call __pthread_exit (0). (This is also implemented in a rather sad way that most likely wouldn't work on x86_64-gnu; I'll get to fixing that some time...) But it doesn't seem to either do any unwinding, nor is __pthread_setcancelstate async-cancel-safe (it uses a mutex). > If you need async cancellation support, the core cancellation routine > could be made weak, so that it is linked into the executable only if > pthread_cancel is ever called. Could you please expand on how this all (unwinding, async cancellation) is relevant? Clearly calling error () in a PTHREAD_CANCEL_ASYNCHRONOUS context is undefined behavior since error () is not async-cancel-safe. Sergey
