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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: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
wifi-calibration
Eric W. Biederman 2006-06-26 00:26:01 -07:00 committed by Linus Torvalds
parent df26c40e56
commit cc288738c9
1 changed files with 6 additions and 5 deletions
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11
fs/proc/base.c
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@ -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 @@ done:
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;
}