[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>
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@ -2224,11 +2224,12 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
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* In the case of a seek we start with the leader and walk nr
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* In the case of a seek we start with the leader and walk nr
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* threads past it.
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* threads past it.
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*/
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*/
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static struct task_struct *first_tid(struct task_struct *leader, int tid, int nr)
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static struct task_struct *first_tid(struct task_struct *leader,
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int tid, int nr)
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{
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{
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struct task_struct *pos = NULL;
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struct task_struct *pos = NULL;
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read_lock(&tasklist_lock);
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rcu_read_lock();
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/* Attempt to start with the pid of a thread */
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/* Attempt to start with the pid of a thread */
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if (tid && (nr > 0)) {
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if (tid && (nr > 0)) {
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pos = find_task_by_pid(tid);
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pos = find_task_by_pid(tid);
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@ -2258,7 +2259,7 @@ static struct task_struct *first_tid(struct task_struct *leader, int tid, int nr
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}
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}
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pos = NULL;
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pos = NULL;
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done:
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done:
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read_unlock(&tasklist_lock);
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rcu_read_unlock();
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return pos;
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return pos;
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}
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}
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@ -2271,7 +2272,7 @@ done:
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static struct task_struct *next_tid(struct task_struct *start)
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static struct task_struct *next_tid(struct task_struct *start)
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{
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{
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struct task_struct *pos;
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struct task_struct *pos;
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read_lock(&tasklist_lock);
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rcu_read_lock();
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pos = start;
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pos = start;
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if (pid_alive(start))
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if (pid_alive(start))
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pos = next_thread(start);
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pos = next_thread(start);
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@ -2279,7 +2280,7 @@ static struct task_struct *next_tid(struct task_struct *start)
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get_task_struct(pos);
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get_task_struct(pos);
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else
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else
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pos = NULL;
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pos = NULL;
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read_unlock(&tasklist_lock);
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rcu_read_unlock();
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put_task_struct(start);
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put_task_struct(start);
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return pos;
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return pos;
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}
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}
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