I found signal handling is still broken in CURRENT source.
the following program demostrates the bug is still in kernel:
#include <stdio.h>
#include <signal.h>
void handler(int sig)
{
signal(SIGTSTP, SIG_DFL);
kill(getpid(), SIGTSTP);
}
int main()
{
char buf[64];
signal(SIGTSTP, handler);
kill(getpid(), SIGTSTP);
printf("input foo:");
scanf("%63s", buf);
printf("you input:%s\n", buf);
return 0;
}
when I press CTRL+Z, the program does not suspend and directly exits.
ktrace indicates that the program directly exits in kernel without
calling exit() from program.
I found SA_STOP handling is disabled in issignal(), delayed SIGTSTP
is forgotten by kernel, this is the reason why SIGTSTP signal handling
is broken. at least, one program is affected --- ftp, run ftp
client program, when 'ftp>' prompt appears, pressing CTRL+Z, causes ftp
to exit and do not suspend. patch:
--- kern_sig.c.old Sun Jul 21 15:38:00 2002
+++ kern_sig.c Sun Jul 21 16:31:02 2002
@@ -1657,7 +1657,7 @@
#endif
break; /* == ignore */
}
-#if 0
+
/*
* If there is a pending stop signal to process
* with default action, stop here,
@@ -1679,16 +1679,10 @@
PROC_UNLOCK(p->p_pptr);
mtx_lock_spin(&sched_lock);
stop(p);
- PROC_UNLOCK(p);
- DROP_GIANT();
- p->p_stats->p_ru.ru_nivcsw++;
- mi_switch();
mtx_unlock_spin(&sched_lock);
- PICKUP_GIANT();
- PROC_LOCK(p);
break;
} else
-#endif
+
if (prop & SA_IGNORE) {
/*
* Except for SIGCONT, shouldn't get here.
David Xu
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