The patch titled
ptrace: simplify ptrace_exit()->ignoring_children() path
has been added to the -mm tree. Its filename is
ptrace-simplify-ptrace_exit-ignoring_children-path.patch
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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: ptrace: simplify ptrace_exit()->ignoring_children() path
From: Oleg Nesterov <oleg@xxxxxxxxxx>
ignoring_children() takes parent->sighand->siglock and checks
k_sigaction[SIGCHLD] atomically. But this buys nothing, we can't get the
"really" wrong result even if we race with sigaction(SIGCHLD). If we read
the "stale" sa_handler/sa_flags we can pretend it was changed right after
the check.
Remove spin_lock(->siglock), and kill "int ign" which caches the result of
ignoring_children() which becomes rather trivial.
Perhaps it makes sense to export this helper, do_notify_parent() can use
it too.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Jerome Marchand <jmarchan@xxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/exit.c | 25 ++++++-------------------
1 file changed, 6 insertions(+), 19 deletions(-)
diff -puN kernel/exit.c~ptrace-simplify-ptrace_exit-ignoring_children-path kernel/exit.c
--- a/kernel/exit.c~ptrace-simplify-ptrace_exit-ignoring_children-path
+++ a/kernel/exit.c
@@ -729,20 +729,12 @@ static void exit_mm(struct task_struct *
}
/*
- * Return nonzero if @parent's children should reap themselves.
- *
- * Called with write_lock_irq(&tasklist_lock) held.
+ * Return nonzero if childs should reap themselves.
*/
-static int ignoring_children(struct task_struct *parent)
+static int ignoring_children(struct sighand_struct *sigh)
{
- int ret;
- struct sighand_struct *psig = parent->sighand;
- unsigned long flags;
- spin_lock_irqsave(&psig->siglock, flags);
- ret = (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
- (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT));
- spin_unlock_irqrestore(&psig->siglock, flags);
- return ret;
+ return sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
+ sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT;
}
/*
@@ -754,7 +746,6 @@ static int ignoring_children(struct task
static void ptrace_exit(struct task_struct *parent, struct list_head *dead)
{
struct task_struct *p, *n;
- int ign = -1;
list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) {
__ptrace_unlink(p);
@@ -776,12 +767,8 @@ static void ptrace_exit(struct task_stru
if (!task_detached(p) && thread_group_empty(p)) {
if (!same_thread_group(p->real_parent, parent))
do_notify_parent(p, p->exit_signal);
- else {
- if (ign < 0)
- ign = ignoring_children(parent);
- if (ign)
- p->exit_signal = -1;
- }
+ else if (ignoring_children(parent->sighand))
+ p->exit_signal = -1;
}
if (task_detached(p)) {
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
linux-next.patch
wait-prevent-exclusive-waiter-starvation.patch
pipe_rdwr_fasync-fix-the-error-handling-to-prevent-the-leak-crash.patch
get_mm_hiwater_xxx-trivial-s-define-inline.patch
getrusage-fill-ru_maxrss-value.patch
ptrace-kill-__ptrace_detach-fix-exit_state-check.patch
ptrace-simplify-ptrace_exit-ignoring_children-path.patch
ptrace-reintroduce-__ptrace_detach-as-a-callee-of-ptrace_exit.patch
ptrace-fix-possible-zombie-leak-on-ptrace_detach.patch
kthread-dont-looking-for-a-task-in-create_kthread-2.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu-fix.patch
pids-improve-get_task_pid-to-fix-the-unsafe-sys_wait4-task_pgrp.patch
pids-refactor-vnr-nr_ns-helpers-to-make-them-safe.patch
pids-kill-now-unused-signal_struct-__pgrp-__session-and-friends.patch
--
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