lkml.org 
[lkml]   [2014]   [Nov]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH -mm 2/3] exit: reparent: call forget_original_parent() under tasklist_lock
Shift "release dead children" loop from forget_original_parent() to
its caller, exit_notify(). It is safe to reap them even if our parent
reaps us right after we drop tasklist_lock, those children no longer
have any connection to the exiting task.

And this allows us to avoid write_lock_irq(tasklist_lock) right after
it was released by forget_original_parent(), we can simply call it
with tasklist_lock held.

While at it, move the comment about forget_original_parent() up to
this function.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/exit.c | 47 +++++++++++++++++++++++------------------------
1 files changed, 23 insertions(+), 24 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 81b62f8..ccf27cb 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -560,19 +560,26 @@ static void reparent_leader(struct task_struct *father, struct task_struct *p,
kill_orphaned_pgrp(p, father);
}

-static void forget_original_parent(struct task_struct *father)
+/*
+ * This does two things:
+ *
+ * A. Make init inherit all the child processes
+ * B. Check to see if any process groups have become orphaned
+ * as a result of our exiting, and if they have any stopped
+ * jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
+ */
+static void forget_original_parent(struct task_struct *father,
+ struct list_head *dead)
{
- struct task_struct *p, *t, *n, *reaper;
- LIST_HEAD(dead_children);
+ struct task_struct *p, *t, *reaper;

- write_lock_irq(&tasklist_lock);
if (unlikely(!list_empty(&father->ptraced)))
- exit_ptrace(father, &dead_children);
+ exit_ptrace(father, dead);

/* Can drop and reacquire tasklist_lock */
reaper = find_child_reaper(father);
if (list_empty(&father->children))
- goto unlock;
+ return;

reaper = find_new_reaper(father, reaper);
list_for_each_entry(p, &father->children, sibling) {
@@ -590,16 +597,9 @@ static void forget_original_parent(struct task_struct *father)
* notify anyone anything has happened.
*/
if (!same_thread_group(reaper, father))
- reparent_leader(father, p, &dead_children);
+ reparent_leader(father, p, dead);
}
list_splice_tail_init(&father->children, &reaper->children);
- unlock:
- write_unlock_irq(&tasklist_lock);
-
- list_for_each_entry_safe(p, n, &dead_children, ptrace_entry) {
- list_del_init(&p->ptrace_entry);
- release_task(p);
- }
}

/*
@@ -609,18 +609,12 @@ static void forget_original_parent(struct task_struct *father)
static void exit_notify(struct task_struct *tsk, int group_dead)
{
bool autoreap;
-
- /*
- * This does two things:
- *
- * A. Make init inherit all the child processes
- * B. Check to see if any process groups have become orphaned
- * as a result of our exiting, and if they have any stopped
- * jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
- */
- forget_original_parent(tsk);
+ struct task_struct *p, *n;
+ LIST_HEAD(dead);

write_lock_irq(&tasklist_lock);
+ forget_original_parent(tsk, &dead);
+
if (group_dead)
kill_orphaned_pgrp(tsk->group_leader, NULL);

@@ -644,6 +638,11 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
wake_up_process(tsk->signal->group_exit_task);
write_unlock_irq(&tasklist_lock);

+ list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
+ list_del_init(&p->ptrace_entry);
+ release_task(p);
+ }
+
/* If the process is dead, release it - nobody will wait for it */
if (autoreap)
release_task(tsk);
--
1.5.5.1


\
 
 \ /
  Last update: 2014-11-20 20:01    [W:0.257 / U:4.276 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site