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authorTejun Heo <tj@kernel.org>2011-03-23 10:37:00 +0100
committerTejun Heo <tj@kernel.org>2011-03-23 10:37:00 +0100
commit39efa3ef3a376a4e53de2f82fc91182459d34200 (patch)
treef75a44fa77396edcf74e41686912554f96681340 /fs
parente5c1902e9260a0075ea52cb5ef627a8d9aaede89 (diff)
signal: Use GROUP_STOP_PENDING to stop once for a single group stop
Currently task->signal->group_stop_count is used to decide whether to stop for group stop. However, if there is a task in the group which is taking a long time to stop, other tasks which are continued by ptrace would repeatedly stop for the same group stop until the group stop is complete. Conversely, if a ptraced task is in TASK_TRACED state, the debugger won't get notified of group stops which is inconsistent compared to the ptraced task in any other state. This patch introduces GROUP_STOP_PENDING which tracks whether a task is yet to stop for the group stop in progress. The flag is set when a group stop starts and cleared when the task stops the first time for the group stop, and consulted whenever whether the task should participate in a group stop needs to be determined. Note that now tasks in TASK_TRACED also participate in group stop. This results in the following behavior changes. * For a single group stop, a ptracer would see at most one stop reported. * A ptracee in TASK_TRACED now also participates in group stop and the tracer would get the notification. However, as a ptraced task could be in TASK_STOPPED state or any ptrace trap could consume group stop, the notification may still be missing. These will be addressed with further patches. * A ptracee may start a group stop while one is still in progress if the tracer let it continue with stop signal delivery. Group stop code handles this correctly. Oleg: * Spotted that a task might skip signal check even when its GROUP_STOP_PENDING is set. Fixed by updating recalc_sigpending_tsk() to check GROUP_STOP_PENDING instead of group_stop_count. * Pointed out that task->group_stop should be cleared whenever task->signal->group_stop_count is cleared. Fixed accordingly. * Pointed out the behavior inconsistency between TASK_TRACED and RUNNING and the last behavior change. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/exec.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 5e62d26a4fe..8328beb9016 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1659,6 +1659,7 @@ static int zap_process(struct task_struct *start, int exit_code)
t = start;
do {
+ task_clear_group_stop_pending(t);
if (t != current && t->mm) {
sigaddset(&t->pending.signal, SIGKILL);
signal_wake_up(t, 1);