Hi, I know the vfork guarantees the children run first. I am just curious why sched_child_runs_first doesn't work. If there is a chance that child process run first, I would be more glade, since I guess that how it works, works with probability. However I tried more the 30+ times, the result was always father process ran first. Eventhough I have't tried that much, I guess my result still told the truth --- sched_child_runs_first doesn't work at all. On Fri, Dec 8, 2017 at 3:50 PM, Alexander Kapshuk <alexander.kapshuk@xxxxxxxxx> wrote: > If my understanding of what Linus says in the post referenced below > is correct, there's never a guarantee which process would run first, > parent or child. > http://yarchive.net/comp/linux/child-runs-first.html > > vfork(), on the other hand, is said in the post to always run the > child process first. See below for an example. > #include <stdio.h> > #include <unistd.h> > #include <sys/time.h> > #include <stdlib.h> > > int main(void) > { > struct timeval tv; > > switch(vfork()) { > case -1: > perror("vfork failed\n"); > exit(-1); > case 0: > if (gettimeofday(&tv, NULL) == 0) > printf("child time sec %ld, usec %ld\n", > tv.tv_sec, tv.tv_usec); > exit(0); > default: > if (gettimeofday(&tv, NULL) == 0) > printf("parent time sec %ld, usec %ld\n", > tv.tv_sec, tv.tv_usec); > } > return 0; > } > > Sample run: > ./gettimeofday > child time sec 1512719270, usec 716672 > parent time sec 1512719270, usec 716748 -- Cheers, Rock _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
