Messages in this thread | | | Date | Fri, 21 Feb 2003 16:22:27 +0100 | From | Stelian Pop <> | Subject | call_usermodehelper signals bug ? |
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Hi,
I think there is a bug involved somewhere in the signal treatment for a program launched via the new call_usermodehelper, but I have trouble trying to pinpoint it.
The problem is visible on my RedHat 8.0 scripts, when I insert a pcmcia network card. This in turn launches hotplug, which launches /sbin/ifup, which launches /sbin/arping, which never ends (although he should end upon reception of 3 times SIGALRM, triggered by alarm(1)): # strace -p 2588 recvfrom(0, "\0\1\10\0\6\4\0\1\0P\4\2\304\304QP\365\222\0\0\0\0\0\0"..., 4096, 0, {sin_family=AF_PACKET, proto=0x806, if3, pkttype=1, addr(6)={1, }, [20]) = 46 rt_sigprocmask(SIG_BLOCK, [INT ALRM], ~[KILL CHLD STOP], 8) = 0 gettimeofday({1045840191, 536542}, NULL) = 0 rt_sigprocmask(SIG_SETMASK, ~[KILL CHLD STOP], NULL, 8) = 0 recvfrom(0, "\0\1\10\0\6\4\0\1\0P\4\2\304\304QP\365\222\0\0\0\0\0\0"..., 4096, 0, {sin_family=AF_PACKET, proto=0x806, if3, pkttype=1, addr(6)={1, }, [20]) = 46 rt_sigprocmask(SIG_BLOCK, [INT ALRM], ~[KILL CHLD STOP], 8) = 0 gettimeofday({1045840192, 528618}, NULL) = 0 rt_sigprocmask(SIG_SETMASK, ~[KILL CHLD STOP], NULL, 8) = 0
As a result, the network doesn't come up at all.
I succeded in reproducing the bug with a simple module which calls call_usermodehelper and a foo.c program which uses SIGALRM (derived from arping source code).
I feel that this has something to do with the elimination of sigemptyset(&curtask->blocked); flush_signals(curtask); flush_signal_handlers(curtask); recalc_sigpending(curtask); in call_usermodehelper() with the new implementation but I'm not expert in this area.
Here is the simple module: #include <linux/module.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/kmod.h>
static int test_init(void) { char *argv[2], *envp[1]; argv[0] = "/tmp/foo"; argv[1] = 0; envp[0] = 0; return call_usermodehelper(argv [0], argv, envp, 0); } module_init(test_init);
And the usermode program: #include <sys/signal.h> #include <unistd.h> #include <stdio.h>
void set_signal(int signo, void (*handler)(void)) { struct sigaction sa; memset(&sa, 0, sizeof(sa)); sa.sa_handler = (void (*)(int))handler; sa.sa_flags = SA_RESTART; sigaction(signo, &sa, NULL); } void catcher(void) { static int count = 0; printf("Here\n"); if (++count == 3) exit(0); alarm(1); } int main(int argc, char **argv) { set_signal(SIGALRM, catcher); catcher(); while(1) { sleep(1); } }
Does this ring a bell to someone ?
Thanks,
Stelian. -- Stelian Pop <stelian.pop@fr.alcove.com> Alcove - http://www.alcove.com - 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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