On Tue 23-08-16 18:32:34, Oleg Nesterov wrote:

On 08/23, Michal Hocko wrote:

quoted

--- a/kernel/fork.c
+++ b/kernel/fork.c

@@ -913,14 +913,11 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 	deactivate_mm(tsk, mm);
 
 	/*
-	 * If we're exiting normally, clear a user-space tid field if
-	 * requested.  We leave this alone when dying by signal, to leave
-	 * the value intact in a core dump, and to save the unnecessary
-	 * trouble, say, a killed vfork parent shouldn't touch this mm.
-	 * Userland only wants this done for a sys_exit.
+	 * Signal userspace if we're not exiting with a core dump
+	 * or a killed vfork parent which shouldn't touch this mm.

Well. ACK, but the comment looks wrong...

The "killed vfork parent ..." part should be removed, as you pointed
out this is no longer true.

OTOH, to me it would be better to not remove the "leave the value
intact in a core dump" part, otherwise the " we're not exiting with
a core dump" looks pointless because SIGNAL_GROUP_COREDUMP is self-
documenting.

Sounds better?

diff --git a/kernel/fork.c b/kernel/fork.c
index b89f0eb99f0a..ddde5849df81 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c

@@ -914,7 +914,8 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 
 	/*
 	 * Signal userspace if we're not exiting with a core dump
-	 * or a killed vfork parent which shouldn't touch this mm.
+	 * because we want to leave the value intact for debugging
+	 * purposes.
 	 */
 	if (tsk->clear_child_tid) {
 		if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&

-- 
Michal Hocko
SUSE Labs

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