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);
}
}
-
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This archive was generated by hypermail 2b29 : Fri Mar 15 2002 - 22:00:14 EST