Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754498AbZIXAno (ORCPT ); Wed, 23 Sep 2009 20:43:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754362AbZIXAnl (ORCPT ); Wed, 23 Sep 2009 20:43:41 -0400 Received: from smtp231.iad.emailsrvr.com ([207.97.245.231]:39153 "EHLO smtp231.iad.emailsrvr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753042AbZIXA3U (ORCPT ); Wed, 23 Sep 2009 20:29:20 -0400 From: Oren Laadan To: Andrew Morton Cc: Linus Torvalds , containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Serge Hallyn , Ingo Molnar , Pavel Emelyanov , Oren Laadan , Oren Laadan Subject: [PATCH v18 28/80] c/r: support for zombie processes Date: Wed, 23 Sep 2009 19:51:08 -0400 Message-Id: <1253749920-18673-29-git-send-email-orenl@librato.com> X-Mailer: git-send-email 1.6.0.4 In-Reply-To: <1253749920-18673-1-git-send-email-orenl@librato.com> References: <1253749920-18673-1-git-send-email-orenl@librato.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9606 Lines: 308 During checkpoint, a zombie processes need only save p->comm, p->state, p->exit_state, and p->exit_code. During restart, zombie processes are created like all other processes. They validate the saved exit_code restore p->comm and p->exit_code. Then they call do_exit() instead of waking up the next task in line. But before, they place the @ctx in p->checkpoint_ctx, so that only at exit time they will wake up the next task in line, and drop the reference to the @ctx. This provides the guarantee that when the coordinator's wait completes, all normal tasks completed their restart, and all zombie tasks are already zombified (as opposed to perhap only becoming a zombie). Changelog[v18]: - Fix leak of ckpt_ctx when restoring zombie tasks - Add a few more ckpt_write_err()s Changelog[v17]: - Validate t->exit_signal for both threads and leader - Skip zombies in most of may_checkpoint_task() - Save/restore t->pdeath_signal - Validate ->exit_signal and ->pdeath_signal Signed-off-by: Oren Laadan --- checkpoint/checkpoint.c | 10 ++++-- checkpoint/process.c | 69 +++++++++++++++++++++++++++++++++++----- checkpoint/restart.c | 41 +++++++++++++++++++++-- include/linux/checkpoint.h | 1 + include/linux/checkpoint_hdr.h | 1 + 5 files changed, 107 insertions(+), 15 deletions(-) diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c index fc02436..93d7860 100644 --- a/checkpoint/checkpoint.c +++ b/checkpoint/checkpoint.c @@ -377,7 +377,7 @@ static int may_checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t) ckpt_debug("check %d\n", task_pid_nr_ns(t, ctx->root_nsproxy->pid_ns)); - if (t->state == TASK_DEAD) { + if (t->exit_state == EXIT_DEAD) { __ckpt_write_err(ctx, "TE", "task state EXIT_DEAD\n", -EBUSY); return -EBUSY; } @@ -387,6 +387,10 @@ static int may_checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t) return -EPERM; } + /* zombies are cool (and also don't have nsproxy, below...) */ + if (t->exit_state) + return 0; + /* verify that all tasks belongs to same freezer cgroup */ if (t != current && !in_same_cgroup_freezer(t, ctx->root_freezer)) { __ckpt_write_err(ctx, "TE", "unfrozen or wrong cgroup", -EBUSY); @@ -403,8 +407,8 @@ static int may_checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t) * FIX: for now, disallow siblings of container init created * via CLONE_PARENT (unclear if they will remain possible) */ - if (ctx->root_init && t != root && t->tgid != root->tgid && - t->real_parent == root->real_parent) { + if (ctx->root_init && t != root && + t->real_parent == root->real_parent && t->tgid != root->tgid) { __ckpt_write_err(ctx, "TE", "task is sibling of root", -EINVAL); return -EINVAL; } diff --git a/checkpoint/process.c b/checkpoint/process.c index 330c8d4..62ae72d 100644 --- a/checkpoint/process.c +++ b/checkpoint/process.c @@ -35,12 +35,18 @@ static int checkpoint_task_struct(struct ckpt_ctx *ctx, struct task_struct *t) h->state = t->state; h->exit_state = t->exit_state; h->exit_code = t->exit_code; - h->exit_signal = t->exit_signal; - h->set_child_tid = (unsigned long) t->set_child_tid; - h->clear_child_tid = (unsigned long) t->clear_child_tid; + if (t->exit_state) { + /* zombie - skip remaining state */ + BUG_ON(t->exit_state != EXIT_ZOMBIE); + } else { + /* FIXME: save remaining relevant task_struct fields */ + h->exit_signal = t->exit_signal; + h->pdeath_signal = t->pdeath_signal; - /* FIXME: save remaining relevant task_struct fields */ + h->set_child_tid = (unsigned long) t->set_child_tid; + h->clear_child_tid = (unsigned long) t->clear_child_tid; + } ret = ckpt_write_obj(ctx, &h->h); ckpt_hdr_put(ctx, h); @@ -172,6 +178,11 @@ int checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t) if (ret < 0) goto out; + + /* zombie - we're done here */ + if (t->exit_state) + return 0; + ret = checkpoint_thread(ctx, t); ckpt_debug("thread %d\n", ret); if (ret < 0) @@ -191,6 +202,19 @@ int checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t) * Restart */ +static inline int valid_exit_code(int exit_code) +{ + if (exit_code >= 0x10000) + return 0; + if (exit_code & 0xff) { + if (exit_code & ~0xff) + return 0; + if (!valid_signal(exit_code & 0xff)) + return 0; + } + return 1; +} + /* read the task_struct into the current task */ static int restore_task_struct(struct ckpt_ctx *ctx) { @@ -202,15 +226,39 @@ static int restore_task_struct(struct ckpt_ctx *ctx) if (IS_ERR(h)) return PTR_ERR(h); + ret = -EINVAL; + if (h->state == TASK_DEAD) { + if (h->exit_state != EXIT_ZOMBIE) + goto out; + if (!valid_exit_code(h->exit_code)) + goto out; + t->exit_code = h->exit_code; + } else { + if (h->exit_code) + goto out; + if ((thread_group_leader(t) && !valid_signal(h->exit_signal)) || + (!thread_group_leader(t) && h->exit_signal != -1)) + goto out; + if (!valid_signal(h->pdeath_signal)) + goto out; + + /* FIXME: restore remaining relevant task_struct fields */ + t->exit_signal = h->exit_signal; + t->pdeath_signal = h->pdeath_signal; + + t->set_child_tid = + (int __user *) (unsigned long) h->set_child_tid; + t->clear_child_tid = + (int __user *) (unsigned long) h->clear_child_tid; + } + memset(t->comm, 0, TASK_COMM_LEN); ret = _ckpt_read_string(ctx, t->comm, TASK_COMM_LEN); if (ret < 0) goto out; - t->set_child_tid = (int __user *) (unsigned long) h->set_child_tid; - t->clear_child_tid = (int __user *) (unsigned long) h->clear_child_tid; - - /* FIXME: restore remaining relevant task_struct fields */ + /* return 1 for zombie, 0 otherwise */ + ret = (h->state == TASK_DEAD ? 1 : 0); out: ckpt_hdr_put(ctx, h); return ret; @@ -330,6 +378,11 @@ int restore_task(struct ckpt_ctx *ctx) ckpt_debug("task %d\n", ret); if (ret < 0) goto out; + + /* zombie - we're done here */ + if (ret) + goto out; + ret = restore_thread(ctx); ckpt_debug("thread %d\n", ret); if (ret < 0) diff --git a/checkpoint/restart.c b/checkpoint/restart.c index 4da09b7..d43eec7 100644 --- a/checkpoint/restart.c +++ b/checkpoint/restart.c @@ -473,17 +473,14 @@ do { \ static int restore_activate_next(struct ckpt_ctx *ctx) { struct task_struct *task; - int active; pid_t pid; - active = ++ctx->active_pid; - if (active >= ctx->nr_pids) { + if (++ctx->active_pid >= ctx->nr_pids) { complete(&ctx->complete); return 0; } pid = get_active_pid(ctx); - ckpt_debug("active pid %d (%d < %d)\n", pid, active, ctx->nr_pids); rcu_read_lock(); task = find_task_by_pid_ns(pid, ctx->root_nsproxy->pid_ns); @@ -511,6 +508,8 @@ static int wait_task_active(struct ckpt_ctx *ctx) ret = wait_event_interruptible(ctx->waitq, is_task_active(ctx, pid) || ckpt_test_ctx_error(ctx)); + ckpt_debug("active %d < %d (ret %d)\n", + ctx->active_pid, ctx->nr_pids, ret); if (!ret && ckpt_test_ctx_error(ctx)) { force_sig(SIGKILL, current); ret = -EBUSY; @@ -567,6 +566,8 @@ static int do_restore_task(void) return -EAGAIN; } + current->flags |= PF_RESTARTING; + /* wait for our turn, do the restore, and tell next task in line */ ret = wait_task_active(ctx); if (ret < 0) @@ -576,6 +577,16 @@ static int do_restore_task(void) if (ret < 0) goto out; + /* + * zombie: we're done here; do_exit() will notice the @ctx on + * our current->checkpoint_ctx (and our PF_RESTARTING) - it + * will call restore_activate_next() and release the @ctx. + */ + if (ret) { + ckpt_ctx_put(ctx); + do_exit(current->exit_code); + } + ret = restore_activate_next(ctx); if (ret < 0) goto out; @@ -592,6 +603,7 @@ static int do_restore_task(void) wake_up_all(&ctx->waitq); } + current->flags &= ~PF_RESTARTING; ckpt_ctx_put(ctx); return ret; } @@ -929,3 +941,24 @@ long do_restart(struct ckpt_ctx *ctx, pid_t pid) return ret; } + +/** + * exit_checkpoint - callback from do_exit to cleanup checkpoint state + * @tsk: terminating task + */ +void exit_checkpoint(struct task_struct *tsk) +{ + struct ckpt_ctx *ctx; + + /* no one else will touch this, because @tsk is dead already */ + ctx = xchg(&tsk->checkpoint_ctx, NULL); + + /* restarting zombies will activate next task in restart */ + if (tsk->flags & PF_RESTARTING) { + BUG_ON(ctx->active_pid == -1); + if (restore_activate_next(ctx) < 0) + pr_warning("c/r: [%d] failed zombie exit\n", tsk->pid); + } + + ckpt_ctx_put(ctx); +} diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h index 4227b31..5c02d9b 100644 --- a/include/linux/checkpoint.h +++ b/include/linux/checkpoint.h @@ -96,6 +96,7 @@ extern long do_checkpoint(struct ckpt_ctx *ctx, pid_t pid); extern long do_restart(struct ckpt_ctx *ctx, pid_t pid); /* task */ +extern int ckpt_activate_next(struct ckpt_ctx *ctx); extern int checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t); extern int restore_task(struct ckpt_ctx *ctx); diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h index 26e10fb..8ae3bbe 100644 --- a/include/linux/checkpoint_hdr.h +++ b/include/linux/checkpoint_hdr.h @@ -132,6 +132,7 @@ struct ckpt_hdr_task { __u32 exit_state; __u32 exit_code; __u32 exit_signal; + __u32 pdeath_signal; __u64 set_child_tid; __u64 clear_child_tid; -- 1.6.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/