From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Fri, 25 Jul 2008 08:47:42 +0000 (-0700)
Subject: coredump: turn core_state->nr_threads into atomic_t
X-Git-Tag: v2.6.27-rc1~341
X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=commitdiff_plain;h=c5f1cc8c1828486a61ab3e575da6e2c62b34d399

coredump: turn core_state->nr_threads into atomic_t

Turn core_state->nr_threads into atomic_t and kill now unneeded
down_write(&mm->mmap_sem) in exit_mm().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/fs/exec.c b/fs/exec.c
index c74bb34..15d493f 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1591,7 +1591,7 @@ static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
 	}
 	rcu_read_unlock();
 done:
-	core_state->nr_threads = nr;
+	atomic_set(&core_state->nr_threads, nr);
 	return nr;
 }
 
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index c0b1747..ae99a28 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -160,7 +160,7 @@ struct vm_area_struct {
 };
 
 struct core_state {
-	int nr_threads;
+	atomic_t nr_threads;
 	struct completion startup;
 };
 
diff --git a/kernel/exit.c b/kernel/exit.c
index 988e232..63d8295 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -678,10 +678,9 @@ static void exit_mm(struct task_struct * tsk)
 	down_read(&mm->mmap_sem);
 	if (mm->core_state) {
 		up_read(&mm->mmap_sem);
-		down_write(&mm->mmap_sem);
-		if (!--mm->core_state->nr_threads)
+
+		if (atomic_dec_and_test(&mm->core_state->nr_threads))
 			complete(&mm->core_state->startup);
-		up_write(&mm->mmap_sem);
 
 		wait_for_completion(&mm->core_done);
 		down_read(&mm->mmap_sem);