Messages in this thread | | | Date | Mon, 22 Aug 2011 14:28:35 +0200 | From | Daniel Lezcano <> | Subject | Re: [PATCH 0/2] Send a SIGCHLD to the init's pid namespace parent when reboot |
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On 08/19/2011 05:24 PM, Oleg Nesterov wrote: > On 08/19, Daniel Lezcano wrote: >> On 08/15/2011 04:47 PM, Oleg Nesterov wrote: >>> - sys_reboot(cmd) does >>> >>> if (!global_namespace) { >>> task_active_pid_ns(current)->reboot_cmd = cmd; >>> sigkill_my_init(); >>> } >> Hi Oleg, >> >> what would be your advice to get rid of from_ancestor_ns which prevent >> the signal to be delivered to the init process ? > Sure, a plain kill can't work. You can do force_sig_info(), this clears > SIGNAL_UNKILLABLE. > > Hmm. But now I seem to recall we have other reasons to make the new > sigkill_task() helper... We will see. Anyway, force_ should work afaics.
Thanks Oleg.
I wrote the patch by sending a signal to the init process of the pid namespace using force_sig_info. That works fine, thanks for the hint.
I am wondering what is the best way to transmit the reason of the reboot to the parent of the container's init.
If we pass the reason to the exit_code of the init process, that will be a bit weird as the process is signaled and did not exited no ? Furthermore, how to differentiate an application container (eg. a script) exiting with an error with the same value of a reboot reason ?
Wouldn't make sense to let the user to specify a signal via prctl where the si_code is filled with the reason ?
Without invoking the prctl, the init process is simply killed by the kernel, otherwise we send the signal to the container's init.
From userspace:
void sigreboot(int sig, siginfo_t *si, void *private) { switch(si->si_code) { case LINUX_REBOOT_CMD_RESTART: reboot_container(); break;
case LINUX_REBOOT_CMD_HALT: halt_container(); break;
... } }
struct sigaction sa = { .sa_sigaction = sigreboot, .sa_flags = SA_SIGINFO; } sigaction(SIGUSR1, &sa, NULL);
prctl(PR_SIGREBOOT, SIGUSR1);
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and from the kernel (called from sys_reboot):
int kill_pid_ns(struct pid_namespace *pid_ns, int reason) { struct task_struct *tsk; struct siginfo info;
if (pid_ns->notifier) {
info.si_signo = SIGKILL; info.si_errno = 0; info.si_code = reason; info.si_pid = 0; info.si_uid = 0;
return force_sig_info(notifier->sig, &info, notifier->tsk); }
write_lock_irq(&tasklist_lock); tsk = pid_ns->child_reaper; write_unlock_irq(&tasklist_lock);
info.si_signo = SIGKILL; info.si_errno = 0; info.si_code = SI_KERNEL; info.si_pid = 0; info.si_uid = 0;
return force_sig_info(SIGKILL, &info, tsk); }
Roughly, assuming pid_ns->notifier is reseted when we reparent to the init_pid_ns.init.
What do you think ?
Thanks -- Daniel
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