Running this program results in a segfault. --------------------------------- #include <signal.h> #include <time.h> #include <limits.h> #include <unistd.h> #include <stdio.h> static void sigev_notify(union sigval arg) {} int main() { timer_t timerid; static struct sigevent sevp = { .sigev_notify = SIGEV_THREAD, .sigev_notify_function = sigev_notify }; timer_create(CLOCK_MONOTONIC, &sevp, &timerid); static const struct itimerspec new_value = { .it_interval = { .tv_sec = 0, .tv_nsec = 1000 }, .it_value = { .tv_sec = 0, .tv_nsec = 1000 } }; timer_settime(&timerid, 0, &new_value, NULL); sleep(UINT_MAX); } --------------------------------- The problem happens when SIGEV_THREAD is used with a too low timer interval. Seems to be related to the new thread stack allocation, but I didn't check in detail. Maybe the problem can be reproduced without using timers, just using pthread_create() in a for loop in a pair of threads, but I have not tried.
If you slow down the application even slightly with strace it works. Similarly with gdb when you slow it down to send thread creation events it works. Filed upstream: https://sourceware.org/bugzilla/show_bug.cgi?id=20340 This needs deeper investigation by the community.
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I'm actually unable to reproduce this in Fedora 26 (glibc 2.25).