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Commit cc288738 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Linus Torvalds
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[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: default avatarEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent df26c40e

fs/proc/base.c

+6 −5
Original line number Diff line number Diff line
@@ -2224,11 +2224,12 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir) 
 * 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 @@ static struct task_struct *first_tid(struct task_struct *leader, int tid, int nr 
	}

	pos = NULL;

done:

	read_unlock(&tasklist_lock);

	rcu_read_unlock();

	return pos;

}
@@ -2271,7 +2272,7 @@ static struct task_struct *first_tid(struct task_struct *leader, int tid, int nr 
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 @@ static struct task_struct *next_tid(struct task_struct *start) 
		get_task_struct(pos);

	else

		pos = NULL;

	read_unlock(&tasklist_lock);

	rcu_read_unlock();

	put_task_struct(start);

	return pos;

}