[PATCH] simply fix first_tgid

Like the bug Oleg spotted in first_tid there was also a small off by one
error in first_tgid, when a seek was done on the /proc directory.  This
fixes that and changes the code structure to make it a little more obvious
what is going on.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 13 insertions, 15 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 8180579f8792..bbcaef9adb57 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2040,34 +2040,32 @@ out:
  * In the case of a seek we start with &init_task and walk nr
  * threads past it.
  */
-static struct task_struct *first_tgid(int tgid, int nr)
+static struct task_struct *first_tgid(int tgid, unsigned int nr)
 {
-        struct task_struct *pos = NULL;
+        struct task_struct *pos;
         rcu_read_lock();
         if (tgid && nr) {
                 pos = find_task_by_pid(tgid);
-                if (pos && !thread_group_leader(pos))
-                        pos = NULL;
-                if (pos)
-                        nr = 0;
+                if (pos && thread_group_leader(pos))
+                        goto found;
         }
         /* If nr exceeds the number of processes get out quickly */
+        pos = NULL;
         if (nr && nr >= nr_processes())
                 goto done;
 
         /* If we haven't found our starting place yet start with
          * the init_task and walk nr tasks forward.
          */
-        if (!pos && (nr >= 0))
-                pos = next_task(&init_task);
-
-        for (; pos && pid_alive(pos); pos = next_task(pos)) {
-                if (--nr > 0)
-                        continue;
-                get_task_struct(pos);
-                goto done;
+        for (pos = next_task(&init_task); nr > 0; --nr) {
+                pos = next_task(pos);
+                if (pos == &init_task) {
+                        pos = NULL;
+                        goto done;
+                }
         }
-        pos = NULL;
+found:
+        get_task_struct(pos);
 done:
         rcu_read_unlock();
         return pos;