[PATCH] proc: drop tasklist lock in task_state()
task_state() needs tasklist_lock to protect ->parent/->real_parent. However
task->parent points to nowhere only when the actions below happen in order
1) release_task(task)
2) release_task(task->parent)
3) a grace period passed
But 3) implies that the memory ops from 1) should be finished, so pid_alive()
can't be true in such a case.
Otherwise, we don't care if ->parent/->real_parent changes under us.
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>
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 35bd39d..25e917f 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -162,7 +162,7 @@
int g;
struct fdtable *fdt = NULL;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
buffer += sprintf(buffer,
"State:\t%s\n"
"SleepAVG:\t%lu%%\n"
@@ -174,14 +174,13 @@
"Gid:\t%d\t%d\t%d\t%d\n",
get_task_state(p),
(p->sleep_avg/1024)*100/(1020000000/1024),
- p->tgid,
- p->pid, pid_alive(p) ? p->group_leader->real_parent->tgid : 0,
- pid_alive(p) && p->ptrace ? p->parent->pid : 0,
+ p->tgid, p->pid,
+ pid_alive(p) ? rcu_dereference(p->real_parent)->tgid : 0,
+ pid_alive(p) && p->ptrace ? rcu_dereference(p->parent)->pid : 0,
p->uid, p->euid, p->suid, p->fsuid,
p->gid, p->egid, p->sgid, p->fsgid);
- read_unlock(&tasklist_lock);
+
task_lock(p);
- rcu_read_lock();
if (p->files)
fdt = files_fdtable(p->files);
buffer += sprintf(buffer,