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exit: reparent: call forget_original_parent() under tasklist_lock

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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>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Sterling Alexander <stalexan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2014-12-10 15:55:20 -08:00 committed by Linus Torvalds
parent ad9e206aef
commit 482a3767e5
1 changed files with 23 additions and 24 deletions
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47
kernel/exit.c
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@ -560,19 +560,26 @@ static void reparent_leader(struct task_struct *father, struct task_struct *p,
kill_orphaned_pgrp(p, father); 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; struct task_struct *p, *t, *reaper;
LIST_HEAD(dead_children);
write_lock_irq(&tasklist_lock);
if (unlikely(!list_empty(&father->ptraced))) if (unlikely(!list_empty(&father->ptraced)))
exit_ptrace(father, &dead_children); exit_ptrace(father, dead);
/* Can drop and reacquire tasklist_lock */ /* Can drop and reacquire tasklist_lock */
reaper = find_child_reaper(father); reaper = find_child_reaper(father);
if (list_empty(&father->children)) if (list_empty(&father->children))
goto unlock; return;
reaper = find_new_reaper(father, reaper); reaper = find_new_reaper(father, reaper);
list_for_each_entry(p, &father->children, sibling) { 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. * notify anyone anything has happened.
*/ */
if (!same_thread_group(reaper, father)) 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); 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) static void exit_notify(struct task_struct *tsk, int group_dead)
{ {
bool autoreap; bool autoreap;
struct task_struct *p, *n;
/* LIST_HEAD(dead);
* 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);
write_lock_irq(&tasklist_lock); write_lock_irq(&tasklist_lock);
forget_original_parent(tsk, &dead);
if (group_dead) if (group_dead)
kill_orphaned_pgrp(tsk->group_leader, NULL); 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); wake_up_process(tsk->signal->group_exit_task);
write_unlock_irq(&tasklist_lock); 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 the process is dead, release it - nobody will wait for it */
if (autoreap) if (autoreap)
release_task(tsk); release_task(tsk);