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 <[email protected]>
--- rc6-mm1/fs/proc/array.c~3_tstate 2006-09-09 22:48:30.000000000 +0400
+++ rc6-mm1/fs/proc/array.c 2006-09-10 01:15:10.000000000 +0400
@@ -162,7 +162,7 @@ static inline char * task_state(struct t
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 @@ static inline char * task_state(struct t
"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,
-
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