From: Sripathi Kodi <sripathik@in.ibm.com>

This patch makes ptrace_attach use write_trylock_irqsave().

Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/ptrace.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff -puN kernel/ptrace.c~use-write_trylock_irqsave-in-ptrace_attach kernel/ptrace.c
--- a/kernel/ptrace.c~use-write_trylock_irqsave-in-ptrace_attach
+++ a/kernel/ptrace.c
@@ -161,6 +161,7 @@ int ptrace_may_attach(struct task_struct
 int ptrace_attach(struct task_struct *task)
 {
 	int retval;
+	unsigned long flags = 0;
 
 	audit_ptrace(task);
 
@@ -181,9 +182,7 @@ repeat:
 	 * cpu's that may have task_lock).
 	 */
 	task_lock(task);
-	local_irq_disable();
-	if (!write_trylock(&tasklist_lock)) {
-		local_irq_enable();
+	if (!write_trylock_irqsave(&tasklist_lock, flags)) {
 		task_unlock(task);
 		do {
 			cpu_relax();
@@ -211,7 +210,7 @@ repeat:
 	force_sig_specific(SIGSTOP, task);
 
 bad:
-	write_unlock_irq(&tasklist_lock);
+	write_unlock_irqrestore(&tasklist_lock, flags);
 	task_unlock(task);
 out:
 	return retval;
_