diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2012-03-19 17:03:22 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2012-05-11 13:15:03 +0100 |
| commit | 3dc731904fb3bad1d3dbd8870cf4461fb2b31680 (patch) | |
| tree | 3fb32e0b7af07c1120c35c97ea927ec943cd19f9 | |
| parent | 20d6f19dca576a671ab61403c366c7154f802b36 (diff) | |
| download | kernel_samsung_smdk4412-3dc731904fb3bad1d3dbd8870cf4461fb2b31680.zip kernel_samsung_smdk4412-3dc731904fb3bad1d3dbd8870cf4461fb2b31680.tar.gz kernel_samsung_smdk4412-3dc731904fb3bad1d3dbd8870cf4461fb2b31680.tar.bz2 | |
exit_signal: simplify the "we have changed execution domain" logic
commit e636825346b36a07ccfc8e30946d52855e21f681 upstream.
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | fs/exec.c | 3 | ||||
| -rw-r--r-- | kernel/exit.c | 7 |
2 files changed, 4 insertions, 6 deletions
@@ -973,6 +973,9 @@ 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); diff --git a/kernel/exit.c b/kernel/exit.c index e6e01b9..ab66cb0 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -828,14 +828,9 @@ static void exit_notify(struct task_struct *tsk, int group_dead) * If the parent exec id doesn't match the exec id we saved * when we started then we know the parent has changed security * domain. - * - * If our self_exec id doesn't match our parent_exec_id then - * we have changed execution domain as these two values started - * the same after a fork. */ if (thread_group_leader(tsk) && tsk->exit_signal != SIGCHLD && - (tsk->parent_exec_id != tsk->real_parent->self_exec_id || - tsk->self_exec_id != tsk->parent_exec_id)) + tsk->parent_exec_id != tsk->real_parent->self_exec_id) tsk->exit_signal = SIGCHLD; if (unlikely(tsk->ptrace)) { |