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-rw-r--r--fs/proc/base.c104
1 files changed, 35 insertions, 69 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 89c20d9d50b..b18f3773dd4 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2142,72 +2142,43 @@ out_no_task:
}
/*
- * Find the first tgid to return to user space.
+ * Find the first task with tgid >= tgid
*
- * Usually this is just whatever follows &init_task, but if the users
- * buffer was too small to hold the full list or there was a seek into
- * the middle of the directory we have more work to do.
- *
- * In the case of a short read we start with find_task_by_pid.
- *
- * 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, unsigned int nr)
+static struct task_struct *next_tgid(unsigned int tgid)
{
- struct task_struct *pos;
- rcu_read_lock();
- if (tgid && nr) {
- pos = find_task_by_pid(tgid);
- 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.
- */
- for (pos = next_task(&init_task); nr > 0; --nr) {
- pos = next_task(pos);
- if (pos == &init_task) {
- pos = NULL;
- goto done;
- }
- }
-found:
- get_task_struct(pos);
-done:
- rcu_read_unlock();
- return pos;
-}
+ struct task_struct *task;
+ struct pid *pid;
-/*
- * Find the next task in the task list.
- * Return NULL if we loop or there is any error.
- *
- * The reference to the input task_struct is released.
- */
-static struct task_struct *next_tgid(struct task_struct *start)
-{
- struct task_struct *pos;
rcu_read_lock();
- pos = start;
- if (pid_alive(start))
- pos = next_task(start);
- if (pid_alive(pos) && (pos != &init_task)) {
- get_task_struct(pos);
- goto done;
+retry:
+ task = NULL;
+ pid = find_ge_pid(tgid);
+ if (pid) {
+ tgid = pid->nr + 1;
+ task = pid_task(pid, PIDTYPE_PID);
+ /* What we to know is if the pid we have find is the
+ * pid of a thread_group_leader. Testing for task
+ * being a thread_group_leader is the obvious thing
+ * todo but there is a window when it fails, due to
+ * the pid transfer logic in de_thread.
+ *
+ * So we perform the straight forward test of seeing
+ * if the pid we have found is the pid of a thread
+ * group leader, and don't worry if the task we have
+ * found doesn't happen to be a thread group leader.
+ * As we don't care in the case of readdir.
+ */
+ if (!task || !has_group_leader_pid(task))
+ goto retry;
+ get_task_struct(task);
}
- pos = NULL;
-done:
rcu_read_unlock();
- put_task_struct(start);
- return pos;
+ return task;
}
+#define TGID_OFFSET (FIRST_PROCESS_ENTRY + (1 /* /proc/self */))
+
/* for the /proc/ directory itself, after non-process stuff has been done */
int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
@@ -2223,29 +2194,24 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
filp->f_pos++;
nr++;
}
- nr -= 1;
- /* f_version caches the tgid value that the last readdir call couldn't
- * return. lseek aka telldir automagically resets f_version to 0.
- */
- tgid = filp->f_version;
- filp->f_version = 0;
- for (task = first_tgid(tgid, nr);
+ tgid = filp->f_pos - TGID_OFFSET;
+ for (task = next_tgid(tgid);
task;
- task = next_tgid(task), filp->f_pos++) {
+ put_task_struct(task), task = next_tgid(tgid + 1)) {
int len;
ino_t ino;
tgid = task->pid;
+ filp->f_pos = tgid + TGID_OFFSET;
len = snprintf(buf, sizeof(buf), "%d", tgid);
ino = fake_ino(tgid, PROC_TGID_INO);
if (filldir(dirent, buf, len, filp->f_pos, ino, DT_DIR) < 0) {
- /* returning this tgid failed, save it as the first
- * pid for the next readir call */
- filp->f_version = tgid;
put_task_struct(task);
- break;
+ goto out;
}
}
+ filp->f_pos = PID_MAX_LIMIT + TGID_OFFSET;
+out:
return 0;
}