In "subtree" restart (restarting not inside a container), 'restart' uses prctl(PR_DEATH_SIGNAL,...) to ensure proper cleanup should the restart fail prematurely. The death_signal is sent, recursively, to all the descendants of root to force-kill them.
However, dead (dummy) tasks, marked with TASK_DEAD, used to exit during the creation of the task tree. Since the task is not within sys_restart it does not have the PF_RESTARTING, and therefore will send the death_signal its children as it exits. To fix it, we observe that dead tasks are much like ghost tasks: they are expected to terminate from within sys_restart, and before the other tasks may resume execution. So we now treat dead (dummy) tasks similarly to ghost tasks. Signed-off-by: Oren Laadan <[email protected]> --- restart.c | 27 ++++++++------------------- 1 files changed, 8 insertions(+), 19 deletions(-) diff --git a/restart.c b/restart.c index 07ffdc3..b810ca9 100644 --- a/restart.c +++ b/restart.c @@ -1485,10 +1485,12 @@ static int ckpt_propagate_session(struct ckpt_ctx *ctx, struct task *task) * needed. In the second pass the task forks the remainder of the * children. In both passes, a child that is marked TASK_THREAD is * created as a thread and a child that is marked TASK_SIBLING is - * created with parent inheritance. In the third pass, terminated - * tasks and temporary placeholders are cleaned up. Finally, the task - * either terminates if it is marked TASK_DEAD or calls sys_restart() - * which does not return. + * created with parent inheritance. Finally, the task will invoke + * sys_restart() which does not return (if successful). + * + * Tasks marked TASK_DEAD or TASK_GHOST are both destined to terminate + * anyway; both use flag RESTART_GHOST for sys_restart(), which will + * result in a call to do_exit(). */ static int ckpt_make_tree(struct ckpt_ctx *ctx, struct task *task) { @@ -1534,17 +1536,6 @@ static int ckpt_make_tree(struct ckpt_ctx *ctx, struct task *task) } } - /* 3rd pass: bring out your deads ... */ - for (child = task->children; child; child = child->next_sib) { - if (child->flags & TASK_DEAD) { - ret = waitpid(child->rpid, NULL, 0); - if (ret < 0) { - perror("waitpid"); - return -1; - } - } - } - /* are we supposed to exit now ? */ if (task->flags & TASK_DEAD) { ckpt_dbg("pid %d: task dead ... exiting\n", task->pid); @@ -1587,7 +1578,7 @@ static int ckpt_make_tree(struct ckpt_ctx *ctx, struct task *task) * then exit (more precisely, killed). The RESTART_GHOST flag * tells the kernel that they are not to be restored. */ - if (task->flags & TASK_GHOST) + if (task->flags & (TASK_GHOST | TASK_DEAD)) flags |= RESTART_GHOST; /* on success this doesn't return */ @@ -1907,9 +1898,7 @@ static int ckpt_adjust_pids(struct ckpt_ctx *ctx) /* read in 'pid_swap' data and adjust ctx->pids_arr */ for (n = 0; n < ctx->tasks_nr; n++) { - /* don't expect data from dead tasks */ - if (ctx->tasks_arr[n].flags & TASK_DEAD) - continue; + /* get pid info from next task */ ret = read(ctx->pipe_in, &swap, sizeof(swap)); if (ret < 0) ckpt_abort(ctx, "read pipe"); -- 1.6.0.4 _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
