[daniel.lezcano at free.fr: [PATCH 0/1][V5] Handle reboot in a child pid namespace]

[Serge Hallyn]

Hi Stefan,

One of our goals for 12.04 is to have an unmodified precise image
boot in lxc.  We will need this patch in the kernel in order to
be able to do that.

It's gone through quite a few feedback cycles and has Oleg's
ack.

This email has a testcase.

thanks,
-serge

----- Forwarded message from Daniel Lezcano <daniel.lezcano at free.fr> -----

Date: Thu,  5 Jan 2012 10:06:49 +0100
From: Daniel Lezcano <daniel.lezcano at free.fr>
To: akpm at linux-foundation.org
Cc: serge.hallyn at canonical.com, oleg at redhat.com, containers at lists.linux-foundation.org, gkurz at fr.ibm.com,
	linux-kernel at vger.kernel.org, mtk.manpages at gmail.com
Subject: [PATCH 0/1][V5] Handle reboot in a child pid namespace


ChangeLog:
==========

 * V5
    - make static inline function for reboot_pid_ns to return 0 when
      CONFIG_PID_NS is off and do the pid_namespace pointer comparison
      inside the function. That makes the compiler to remove this portion
      of code when CONFIG_PID_NS is not enabled.

 * V4
   - store the signal number the child pid namespace init should
     exit from. It is simpler, cleaner, and does not add more encoding
     bits to the exit code of the process.

 * V3
   - removed lock and serialization of pid_ns_reboot

 * V2
   - added a lock for the pid namespace to prevent racy call
     to the 'reboot' syscall
   - Moved 'reboot' command assigned in zap_pid_ns_processes
     instead of wait_task_zombie
   - added tasklist lock around force_sig
   - added do_exit in pid_ns_reboot
   - used task_active_pid_ns instead of declaring a new variable in sys_reboot
   - moved code up before POWER_OFF changed to HALT in sys_reboot


Test case:
==========

#include <alloca.h>
#include <stdio.h>
#include <sched.h>
#include <unistd.h>
#include <signal.h>
#include <sys/reboot.h>
#include <sys/types.h>
#include <sys/wait.h>

#include <linux/reboot.h>

static int do_reboot(void *arg)
{
        int *cmd = arg;

        if (reboot(*cmd))
                printf("failed to reboot(%d): %m\n", *cmd);
}

int test_reboot(int cmd, int sig)
{
        long stack_size = 4096;
        void *stack = alloca(stack_size) + stack_size;
        int status;
        pid_t ret;

        ret = clone(do_reboot, stack, CLONE_NEWPID | SIGCHLD, &cmd);
        if (ret < 0) {
                printf("failed to clone: %m\n");
                return -1;
        }

        if (wait(&status) < 0) {
                printf("unexpected wait error: %m\n");
                return -1;
        }

        if (!WIFSIGNALED(status)) {
                printf("child process exited but was not signaled\n");
                return -1;
        }

        if (WTERMSIG(status) != sig) {
                printf("signal termination is not the one expected\n");
                return -1;
        }

        return 0;
}

int main(int argc, char *argv[])
{
        int status;

        status = test_reboot(LINUX_REBOOT_CMD_RESTART, SIGHUP);
        if (status < 0)
                return 1;
        printf("reboot(LINUX_REBOOT_CMD_RESTART) succeed\n");

        status = test_reboot(LINUX_REBOOT_CMD_RESTART2, SIGHUP);
        if (status < 0)
                return 1;
        printf("reboot(LINUX_REBOOT_CMD_RESTART2) succeed\n");

        status = test_reboot(LINUX_REBOOT_CMD_HALT, SIGINT);
        if (status < 0)
                return 1;
        printf("reboot(LINUX_REBOOT_CMD_HALT) succeed\n");

        status = test_reboot(LINUX_REBOOT_CMD_POWER_OFF, SIGINT);
        if (status < 0)
                return 1;
        printf("reboot(LINUX_REBOOT_CMD_POWERR_OFF) succeed\n");

        status = test_reboot(LINUX_REBOOT_CMD_CAD_ON, -1);
        if (status >= 0) {
                printf("reboot(LINUX_REBOOT_CMD_CAD_ON) should have failed\n");
                return 1;
        }
        printf("reboot(LINUX_REBOOT_CMD_CAD_ON) has failed as expected\n");

        return 0;
}

Daniel Lezcano (1):
  Add reboot_pid_ns to handle the reboot syscall

 include/linux/pid_namespace.h |    8 +++++++-
 kernel/pid_namespace.c        |   33 +++++++++++++++++++++++++++++++++
 kernel/sys.c                  |    3 +++
 3 files changed, 43 insertions(+), 1 deletions(-)

-- 
1.7.5.4


----- End forwarded message -----