Messages in this thread | | | Date | Sun, 10 Mar 2002 22:08:02 +0100 | Subject | directory notifications lost after fork? | From | Oskar Liljeblad <> |
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The code snipper demonstrates what I consider a bug in the dnotify facilities in the kernel. After a fork, all registered notifications are lost in the process where they originally where registered (the parent process). "lost" here means that the signal specified with F_SETSIG fcntl no longer is delivered when notified.
How to reproduce (tested with 2.4.17): gcc -o dnoticebug dnoticebug.c dnoticebug & # run in background cat dnoticebug.c >/dev/null # "notified" should now be printed cat dnoticebug.c >/dev/null # nothing is printed this time
If you comment out the line with fork below, "notified" *will* be printed every time you cat dnoticebug.c.
I'm not subscribed to the list so I'd appreciate if you CCed me. (Otherwise I'd have to use the archives :) Thanks.
Oskar Liljeblad (oskar@osk.mine.nu)
===
#define _GNU_SOURCE #include <fcntl.h> #include <signal.h> #include <stdio.h> #include <unistd.h>
static void handler(int sig, siginfo_t *si, void *data) { printf("notified\n"); }
int main(void) { struct sigaction act; int fd;
act.sa_sigaction = handler; sigemptyset(&act.sa_mask); act.sa_flags = SA_SIGINFO; sigaction(SIGRTMIN, &act, NULL);
fd = open(".", O_RDONLY); fcntl(fd, F_SETSIG, SIGRTMIN); fcntl(fd, F_NOTIFY, DN_ACCESS|DN_MULTISHOT);
while (1) { pause(); if (fork() <= 0) exit(0); wait(NULL); } } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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