exit_signal: simplify the "we have changed execution domain" logic

exit_notify() checks "tsk->self_exec_id != tsk->parent_exec_id"
to handle the "we have changed execution domain" case.

We can change do_thread() to always set ->exit_signal = SIGCHLD
and remove this check to simplify the code.

We could change setup_new_exec() instead, this looks more logical
because it increments ->self_exec_id. But note that de_thread()
already resets ->exit_signal if it changes the leader, let's keep
both changes close to each other.

Note that we change ->exit_signal lockless, this changes the rules.
Thereafter ->exit_signal is not stable under tasklist but this is
fine, the only possible change is OLDSIG -> SIGCHLD. This can race
with eligible_child() but the race is harmless. We can race with
reparent_leader() which changes our ->exit_signal in parallel, but
it does the same change to SIGCHLD.

The noticeable user-visible change is that the execing task is not
"visible" to do_wait()->eligible_child(__WCLONE) right after exec.
To me this looks more logical, and this is consistent with mt case.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This commit is contained in:

Oleg Nesterov

2012-03-19 17:03:22 +01:00

committed by

Linus Torvalds

parent 5f8aadd8b9

commit e636825346

2 changed files with 4 additions and 6 deletions

									
										fs/exec.c
									
		+3
		
												View File
												
				@@ -977,6 +977,9 @@ static int de_thread(struct task_struct *tsk)

					sig->notify_count = 0;

				no_thread_group:

					/* we have changed execution domain */

					tsk->exit_signal = SIGCHLD;

					if (current->mm)

						setmax_mm_hiwater_rss(&sig->maxrss, current->mm);