[PATCH] proc: Remove tasklist_lock from proc_task_readdir.
This is just like my previous removal of tasklist_lock from first_tgid, and
next_tgid. It simply had to wait until it was rcu safe to walk the thread
list.
This should be the last instance of the tasklist_lock in proc. So user
processes should not be able to influence the tasklist lock hold times.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 7734697..6092a6e 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2224,11 +2224,12 @@
* In the case of a seek we start with the leader and walk nr
* threads past it.
*/
-static struct task_struct *first_tid(struct task_struct *leader, int tid, int nr)
+static struct task_struct *first_tid(struct task_struct *leader,
+ int tid, int nr)
{
struct task_struct *pos = NULL;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
/* Attempt to start with the pid of a thread */
if (tid && (nr > 0)) {
pos = find_task_by_pid(tid);
@@ -2258,7 +2259,7 @@
}
pos = NULL;
done:
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
return pos;
}
@@ -2271,7 +2272,7 @@
static struct task_struct *next_tid(struct task_struct *start)
{
struct task_struct *pos;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
pos = start;
if (pid_alive(start))
pos = next_thread(start);
@@ -2279,7 +2280,7 @@
get_task_struct(pos);
else
pos = NULL;
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
put_task_struct(start);
return pos;
}