Russell King wrote:
>
> On Tue, Mar 19, 2002 at 09:00:21AM +0100, Kasper Dupont wrote:
> >
> > Why actually panic because of an attempt to kill init?
> >
> > Of course a message should be printed, but after that
> > couldn't do_exit enter a loop where it just handles
> > signals and zombies?
>
> Examine the LKML archive around 23rd December 2001, where Alan Cox wrote:
>
> | pid1 ends up trying to kill pid1 and it goes deeply down the toilet from
> | that point onwards. The Unix traditional world reboots when pid 1 dies.
Thank you for pointing that out. But I'm afraid it doesn't
answer my question. I understand that a system where init
has died cannot be expected to continue working like if
nothing was wrong.
What to do in this case might be a matter of taste, of
course a panic or a reboot does make sense. But trying to
recover as much as posible would also make sense. This
could be caused by a problem in userspace, the kernel does
not have to be corrupted already.
If we agree that this is a matter of taste lets not try to
argue about whose taste is the best.
I was really just wondering if the patch below would work.
Well I just tested it, and it did work like I expected. If
I killed init (by replacing /sbin/init with something else
and telling init to reexecute itself) I got the warning.
But the system continued to work.
Of course init would no longer respawn processes, and I
could not change runlevel. But I could login, kill
processes, and remount filesystems read-only. And no
processes became zombies.
-- Kasper Dupont -- der bruger for meget tid på usenet. For sending spam use mailto:razor-report@daimi.au.dk
--- exit.c~ Mon Feb 25 20:38:13 2002 +++ exit.c Tue Mar 19 21:47:58 2002 @@ -429,6 +429,38 @@ write_unlock_irq(&tasklist_lock); } +#define __KERNEL_SYSCALLS__ +#include <linux/unistd.h> +NORET_TYPE void flush_child_loop(struct task_struct *curtask) +{ + struct k_sigaction sa; + daemonize(); + + spin_lock_irq(&curtask->sigmask_lock); + siginitsetinv(&curtask->blocked, sigmask(SIGCHLD)); + recalc_sigpending(curtask); + spin_unlock_irq(&curtask->sigmask_lock); + + /* Install a handler so SIGCLD is delivered */ + sa.sa.sa_handler = SIG_IGN; + sa.sa.sa_flags = 0; + siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD)); + do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0); + + for (;;) { + set_task_state(curtask, TASK_INTERRUPTIBLE); + schedule(); + if (signal_pending(curtask)) { + while (waitpid(-1, (unsigned int *)0, __WALL|WNOHANG) > 0) + ; + spin_lock_irq(&curtask->sigmask_lock); + flush_signals(curtask); + recalc_sigpending(curtask); + spin_unlock_irq(&curtask->sigmask_lock); + } + } +} + NORET_TYPE void do_exit(long code) { struct task_struct *tsk = current; @@ -437,8 +469,10 @@ panic("Aiee, killing interrupt handler!"); if (!tsk->pid) panic("Attempted to kill the idle task!"); - if (tsk->pid == 1) - panic("Attempted to kill init!"); + if (tsk->pid == 1) { + printk(KERN_EMERG "Attempted to kill init!\n"); + flush_child_loop(tsk); + } tsk->flags |= PF_EXITING; del_timer_sync(&tsk->real_timer);
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This archive was generated by hypermail 2b29 : Sat Mar 23 2002 - 22:00:19 EST