A signal delivery to a thread is not working
properly in the kernel when a signal
handler is specified. Here is the case:
A process blocks all signals and registers
a handler for a signal.
A newly created thread unblocks that signal.
When that signal is sent to a process, the
sighandler is not getting called.
(if this signal is sent twice, it works)
I've attached a small test program to reproduce
it using NPTL.
The following patch fixes this problem in kernel.
Please apply.
Thanks,
Saurabh Desai
diff -Naur linux-2.5.59.orig/kernel/signal.c linux-2.5.59/kernel/signal.c
--- linux-2.5.59.orig/kernel/signal.c 2003-01-30 16:54:44.000000000 -0600
+++ linux-2.5.59/kernel/signal.c 2003-01-30 16:55:22.000000000 -0600
@@ -854,11 +854,13 @@
tmp = p->sig->curr_target;
- if (!tmp || tmp->tgid != p->tgid)
+ if (!tmp || tmp->tgid != p->tgid) {
/* restart balancing at this thread */
p->sig->curr_target = p;
+ tmp = p;
+ }
- else for (;;) {
+ for (;;) {
if (thread_group_empty(p))
BUG();
if (!tmp || tmp->tgid != p->tgid)
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <pthread.h>
#include <signal.h>
void sigcatcher(int sig)
{
fprintf(stderr, "The sigcatcher caught signal %d\n", sig);
pthread_exit(0);
}
void *sig_thread(void *p)
{
sigset_t sigs_to_catch;
/* Unblock SIGINT */
sigemptyset(&sigs_to_catch);
sigaddset(&sigs_to_catch, SIGINT);
pthread_sigmask(SIG_UNBLOCK, &sigs_to_catch, NULL);
fprintf(stderr, "sent a SIGINT (ctrl-C) to this process(%d)\n", getpid());
sleep(60);
return (NULL);
}
extern int main(void)
{
pthread_t thread;
sigset_t sigs_to_block;
struct sigaction action;
/* Block all signals */
sigfillset(&sigs_to_block);
pthread_sigmask(SIG_BLOCK, &sigs_to_block, NULL);
/* Set a signal handler */
action.sa_handler = sigcatcher;
action.sa_flags = 0;
sigaction(SIGINT, &action, NULL);
pthread_create(&thread, NULL, sig_thread, NULL);
/* wait until thread is finished */
pthread_join(thread, NULL);
return 0;
}
-
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This archive was generated by hypermail 2b29 : Fri Jan 31 2003 - 22:00:26 EST