reproduce:
static void *pthread(void *arg)
{
system(arg);
}
void test (int argc, char *argv[])
{
pthread_create(&pthread0, &attr, pthread, argv[1]);
pthread_create(&pthread1, &attr, pthread, argv[2]);
}
only one pthread system() returnd, othres hanged
rootcause:
As we known, system() will create a new task called:
system -c XX
The example:
parent group child groups
pthread0 -> waitpid() -> system -c ps -> exit() -> nxtask_signalparent()
pthread1 -> waitpid() -> system -c ls -> exit() -> nxtask_signalparent()
Each child group exit with function nxtask_signalparent(),
As we expect:
system -c ps will signal pthread0
system -c ls will signal pthread1
But actually:
system -c ps will signal pthread0/1
system -c ls will signal pthread0/1
As the spec, we know, this behavior is normal:
https://man7.org/linux/man-pages/man2/sigwaitinfo.2.html
So for this situation, when the signo is SIGCHLD, we broadcast.
Signed-off-by: ligd <liguiding1@xiaomi.com>
1552e52e14