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authorOleg Nesterov <oleg@tv-sign.ru>2006-06-26 00:26:01 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-26 09:58:26 -0700
commita872ff0cb2218dc9688b990c5ccda064dc40946b (patch)
treeff94ae63e668f0229fc7aeed220def7e9708db3a
parentcc288738c9ae3c64d3c50b86604044d1f6d22941 (diff)
[PATCH] simplify/fix first_tid()
first_tid: /* If nr exceeds the number of threads there is nothing todo */ if (nr) { if (nr >= get_nr_threads(leader)) goto done; } This is not reliable: sub-threads can exit after this check, so the 'for' loop below can overlap and proc_task_readdir() can return an already filldir'ed dirents. for (; pos && pid_alive(pos); pos = next_thread(pos)) { if (--nr > 0) continue; Off-by-one error, will return 'leader' when nr == 1. This patch tries to fix these problems and simplify the code. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--fs/proc/base.c38
1 files changed, 17 insertions, 21 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 6092a6e2c5a..5ee46d3a5ca 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2227,38 +2227,34 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
static struct task_struct *first_tid(struct task_struct *leader,
int tid, int nr)
{
- struct task_struct *pos = NULL;
+ struct task_struct *pos;
rcu_read_lock();
/* Attempt to start with the pid of a thread */
if (tid && (nr > 0)) {
pos = find_task_by_pid(tid);
- if (pos && (pos->group_leader != leader))
- pos = NULL;
- if (pos)
- nr = 0;
+ if (pos && (pos->group_leader == leader))
+ goto found;
}
/* If nr exceeds the number of threads there is nothing todo */
- if (nr) {
- if (nr >= get_nr_threads(leader))
- goto done;
- }
+ pos = NULL;
+ if (nr && nr >= get_nr_threads(leader))
+ goto out;
- /* If we haven't found our starting place yet start with the
- * leader and walk nr threads forward.
+ /* If we haven't found our starting place yet start
+ * with the leader and walk nr threads forward.
*/
- if (!pos && (nr >= 0))
- pos = leader;
-
- for (; pos && pid_alive(pos); pos = next_thread(pos)) {
- if (--nr > 0)
- continue;
- get_task_struct(pos);
- goto done;
+ for (pos = leader; nr > 0; --nr) {
+ pos = next_thread(pos);
+ if (pos == leader) {
+ pos = NULL;
+ goto out;
+ }
}
- pos = NULL;
-done:
+found:
+ get_task_struct(pos);
+out:
rcu_read_unlock();
return pos;
}