Date: Sun, 21 Jul 2002 17:02:11 -0700 (PDT) From: David Xu <bsddiy@yahoo.com> To: Julian Elischer <julian@elischer.org> Cc: freebsd-current@freebsd.org Subject: Re: signal handling bug in KSE MIII Message-ID: <20020722000211.55864.qmail@web20902.mail.yahoo.com>
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--- David Xu <bsddiy@yahoo.com> wrote:
> 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
>
OOPS, the extra kill() calling in main() should be removed
in demo program, correct source code is:
#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);
printf("input foo:");
scanf("%63s", buf);
printf("you input:%s\n", buf);
return 0;
}
David Xu
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