diff options
author | Oleg Nesterov <oleg@redhat.com> | 2011-04-07 20:44:11 +0200 |
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committer | Oleg Nesterov <oleg@redhat.com> | 2011-04-07 20:44:11 +0200 |
commit | e46bc9b6fd65bc9f406a4211fbf95683cc9c2937 (patch) | |
tree | 57046f6b2f4674a0c9048ab1ad1ff50fae7e373a /kernel/exit.c | |
parent | 2b9accbee563f535046ff2cd382d0acaa92e130c (diff) | |
parent | 321fb561971ba0f10ce18c0f8a4b9fbfc7cef4b9 (diff) |
Merge branch 'ptrace' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc into ptrace
Diffstat (limited to 'kernel/exit.c')
-rw-r--r-- | kernel/exit.c | 84 |
1 files changed, 67 insertions, 17 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 6a488ad2dce5..5cbc83e83a5d 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1538,33 +1538,83 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace, return 0; } - if (likely(!ptrace) && unlikely(task_ptrace(p))) { + /* dead body doesn't have much to contribute */ + if (p->exit_state == EXIT_DEAD) + return 0; + + /* slay zombie? */ + if (p->exit_state == EXIT_ZOMBIE) { /* - * This child is hidden by ptrace. - * We aren't allowed to see it now, but eventually we will. + * A zombie ptracee is only visible to its ptracer. + * Notification and reaping will be cascaded to the real + * parent when the ptracer detaches. */ - wo->notask_error = 0; - return 0; - } + if (likely(!ptrace) && unlikely(task_ptrace(p))) { + /* it will become visible, clear notask_error */ + wo->notask_error = 0; + return 0; + } - if (p->exit_state == EXIT_DEAD) - return 0; + /* we don't reap group leaders with subthreads */ + if (!delay_group_leader(p)) + return wait_task_zombie(wo, p); - /* - * We don't reap group leaders with subthreads. - */ - if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p)) - return wait_task_zombie(wo, p); + /* + * Allow access to stopped/continued state via zombie by + * falling through. Clearing of notask_error is complex. + * + * When !@ptrace: + * + * If WEXITED is set, notask_error should naturally be + * cleared. If not, subset of WSTOPPED|WCONTINUED is set, + * so, if there are live subthreads, there are events to + * wait for. If all subthreads are dead, it's still safe + * to clear - this function will be called again in finite + * amount time once all the subthreads are released and + * will then return without clearing. + * + * When @ptrace: + * + * Stopped state is per-task and thus can't change once the + * target task dies. Only continued and exited can happen. + * Clear notask_error if WCONTINUED | WEXITED. + */ + if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED))) + wo->notask_error = 0; + } else { + /* + * If @p is ptraced by a task in its real parent's group, + * hide group stop/continued state when looking at @p as + * the real parent; otherwise, a single stop can be + * reported twice as group and ptrace stops. + * + * If a ptracer wants to distinguish the two events for its + * own children, it should create a separate process which + * takes the role of real parent. + */ + if (likely(!ptrace) && task_ptrace(p) && + same_thread_group(p->parent, p->real_parent)) + return 0; + + /* + * @p is alive and it's gonna stop, continue or exit, so + * there always is something to wait for. + */ + wo->notask_error = 0; + } /* - * It's stopped or running now, so it might - * later continue, exit, or stop again. + * Wait for stopped. Depending on @ptrace, different stopped state + * is used and the two don't interact with each other. */ - wo->notask_error = 0; - if (task_stopped_code(p, ptrace)) return wait_task_stopped(wo, ptrace, p); + /* + * Wait for continued. There's only one continued state and the + * ptracer can consume it which can confuse the real parent. Don't + * use WCONTINUED from ptracer. You don't need or want it. + */ return wait_task_continued(wo, p); } |