>From ce9dd2fc7332597d46872f3f8c52ac0806f381d1 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx> Date: Fri, 29 Oct 2010 23:16:10 -0700 Subject: [PATCH 1/1] Mark ghost task as detached earlier During restart() of an application, ghost tasks are be marked as "detached" so they don't send a SIGCHLD to their parent when they exit. But this is currently being done a little too late in the "life" of the ghost and ends up confusing the container-init. Suppose a ghost child of the container-init is waiting in do_ghost_task(). It is not yet detached. If the container-init is terminated for some reason, the container-init sends SIGKILL to its children (including this ghost). The container-init then waits for the un-detached children to exit, expecting to be notified via SIGCHLD. When the ghost-child receives the SIGKILL, it wakes up and marks itself detached and proceeds to exit. Since it is now detached, it will not notify the parent, thus leaving the container-init blocked indefintely. Some background: When running some tests on the C/R code we ran into the problem of the container-init not waiting for detached processes. This problem was extensively discssued here: http://lkml.org/lkml/2010/6/16/295 Eric Biederman had a fix for the problem: http://lkml.org/lkml/2010/7/12/213 When I applied this fix to the C/R tree and repeated the tests, I ran into the above issue of the container-init hanging. Marking the ghost as detached earlier seems to fix the confusion in the container-init. Oren, is there a reason not to mark the ghost task detached earlier than is currently being done ? Signed-off-by: Sukadev Bhattiprolu (sukadev@xxxxxxxxxx) --- kernel/checkpoint/restart.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/checkpoint/restart.c b/kernel/checkpoint/restart.c index 17270b8..95789c0 100644 --- a/kernel/checkpoint/restart.c +++ b/kernel/checkpoint/restart.c @@ -953,6 +953,7 @@ static int do_ghost_task(void) struct ckpt_ctx *ctx; int ret; + current->exit_signal = -1; ctx = wait_checkpoint_ctx(); if (IS_ERR(ctx)) return PTR_ERR(ctx); @@ -972,7 +973,6 @@ static int do_ghost_task(void) if (ret < 0) ckpt_err(ctx, ret, "ghost restart failed\n"); - current->exit_signal = -1; restore_debug_exit(ctx); ckpt_ctx_put(ctx); do_exit(0); -- 1.6.6.1 _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
