clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME) sleeps forever

[tiran]

clock_nanosleep() with monotonic clock and absolute time sleeps forever. strace shows that node is spinning fast in a FUTEX lock.

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.2 (a77b559a8b40b7e89fc8c17e41034128df9543e4)
clang version 14.0.0 (https://github.com/llvm/llvm-project 782c0dd1a1c235afb09a34e7da4a1267ead14765)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /emsdk/upstream/bin

Reproducer:

#define _POSIX_C_SOURCE 200809L
#include <stdio.h>
#include <time.h>

int main(void) {
    struct timespec deadline;
    clock_gettime(CLOCK_MONOTONIC, &deadline);
    deadline.tv_sec += 1;
    fprintf(stdout, "%li\n", time(NULL));
    clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &deadline, NULL);
    fprintf(stdout, "%li\n", time(NULL));
}

$ gcc -o nanosleep nanosleep.c
$ ./nanosleep
1646748808
1646748809

$ emcc -o nanosleep.js nanosleep.c
$ time node nanosleep.js
1646748866
^C

real    0m9.480s
user    0m9.483s
sys     0m0.033s

[sbc100]

Thanks for the report. Do you happen to know if this is a new issue? (I can verify myself, but just curious if you are seeing this pop up in a particular version).

[sbc100]

Some background: It looks like clock_nanosleep was not available prior to recent musl upgrade in #13006. Attempting to compile that code with anything older than 3.0.0 results in an undefined symbol. And it also looks like this runtime infinite loop existed since it was first introduced in #13006.

It looks like we have never supported TIMER_ABSTIME .. I have a fix pending.

[tiran]

Thanks for the report. Do you happen to know if this is a new issue? (I can verify myself, but just curious if you are seeing this pop up in a particular version).

Thank you for the quick fix! I noticed the problem while porting CPython to wasm32-emscripten. I didn't have enough infrastructure working with Emscripten 2. You figured it out before I saw your question.