On Tue, Nov 12, 2019 at 1:52 PM Florian Weimer <fw@xxxxxxxxxxxxx> wrote: > > * enh: > > > On Tue, Nov 12, 2019 at 1:38 PM Florian Weimer <fw@xxxxxxxxxxxxx> wrote: > >> > >> * enh: > >> > >> > POSIX removed ESRCH years ago. > >> > > >> > In resolving http://austingroupbugs.net/view.php?id=1214 it was made > >> > clear that callers can't rely on using signal 0 to test for the > >> > continued existence of a thread. Update the man page to make it clearer > >> > that this doesn't generally work (even if it sometimes seems to). > >> > > >> > See also the long explanation of why this is the case (and how to fix > >> > your code) here: > >> > > >> > https://android.googlesource.com/platform/bionic/+/master/docs/status.md#invalid-handling-targetsdkversion-o > >> > >> Well, if you fix the thread exit race (like musl did, and glibc should > >> as well, see bug 12889), you could get a reliable ESRCH as a side > >> effect. Pity that POSIX doesn't allow that. > > > > this isn't about the tid stored *in* the object that the pthread_t points to. > > > > like i (briefly) said in the commit message, this is because a > > pthread_t is a pointer, so if you have an old pthread_t that's been > > recycled... boom! > > Backing storage for a pthread_t object denoting a joinable thread > cannot be recycled, so that's not the case here. POSIX mandates > returning success even if the implementation has detected that it must > not send the signal because the thread has already terminated. who said anything about joinable? the cases we've seen in practice are that folks incorrectly believe that pthread_kill(3) with a signal of 0 is a reliable way to test whether a thread is still running.
