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authorOleg Nesterov <oleg@tv-sign.ru>2006-10-28 10:38:54 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-28 11:30:54 -0700
commita98b6094261c0112e9c455c96995972181bff049 (patch)
tree01a15d79e331730de5a255a7109cf1318b95f6ac /kernel/taskstats.c
parentb8534d7bd89df0cd41cd47bcd6733a05ea9a691a (diff)
downloadlinaro-lsk-a98b6094261c0112e9c455c96995972181bff049.tar.gz
[PATCH] taskstats: don't use tasklist_lock
Remove tasklist_lock from taskstats.c. find_task_by_pid() is rcu-safe. ->siglock allows us to traverse subthread without tasklist. Q: delay accounting looks wrong to me. If sub-thread has already called taskstats_exit_send() but didn't call release_task(self) yet it will be accounted twice. The window is big. No? Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Shailabh Nagar <nagar@watson.ibm.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Jay Lan <jlan@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/taskstats.c')
-rw-r--r--kernel/taskstats.c59
1 files changed, 24 insertions, 35 deletions
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index b2efda94615..b724aeea544 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -174,21 +174,19 @@ static void send_cpu_listeners(struct sk_buff *skb, unsigned int cpu)
up_write(&listeners->sem);
}
-static int fill_pid(pid_t pid, struct task_struct *pidtsk,
+static int fill_pid(pid_t pid, struct task_struct *tsk,
struct taskstats *stats)
{
int rc = 0;
- struct task_struct *tsk = pidtsk;
- if (!pidtsk) {
- read_lock(&tasklist_lock);
+ if (!tsk) {
+ rcu_read_lock();
tsk = find_task_by_pid(pid);
- if (!tsk) {
- read_unlock(&tasklist_lock);
+ if (tsk)
+ get_task_struct(tsk);
+ rcu_read_unlock();
+ if (!tsk)
return -ESRCH;
- }
- get_task_struct(tsk);
- read_unlock(&tasklist_lock);
} else
get_task_struct(tsk);
@@ -214,40 +212,28 @@ static int fill_pid(pid_t pid, struct task_struct *pidtsk,
}
-static int fill_tgid(pid_t tgid, struct task_struct *tgidtsk,
+static int fill_tgid(pid_t tgid, struct task_struct *first,
struct taskstats *stats)
{
- struct task_struct *tsk, *first;
+ struct task_struct *tsk;
unsigned long flags;
+ int rc = -ESRCH;
/*
* Add additional stats from live tasks except zombie thread group
* leaders who are already counted with the dead tasks
*/
- first = tgidtsk;
- if (!first) {
- read_lock(&tasklist_lock);
+ rcu_read_lock();
+ if (!first)
first = find_task_by_pid(tgid);
- if (!first) {
- read_unlock(&tasklist_lock);
- return -ESRCH;
- }
- get_task_struct(first);
- read_unlock(&tasklist_lock);
- } else
- get_task_struct(first);
+ if (!first || !lock_task_sighand(first, &flags))
+ goto out;
- tsk = first;
- read_lock(&tasklist_lock);
- /* Start with stats from dead tasks */
- if (first->sighand) {
- spin_lock_irqsave(&first->sighand->siglock, flags);
- if (first->signal->stats)
- memcpy(stats, first->signal->stats, sizeof(*stats));
- spin_unlock_irqrestore(&first->sighand->siglock, flags);
- }
+ if (first->signal->stats)
+ memcpy(stats, first->signal->stats, sizeof(*stats));
+ tsk = first;
do {
if (tsk->exit_state == EXIT_ZOMBIE && thread_group_leader(tsk))
continue;
@@ -260,15 +246,18 @@ static int fill_tgid(pid_t tgid, struct task_struct *tgidtsk,
delayacct_add_tsk(stats, tsk);
} while_each_thread(first, tsk);
- read_unlock(&tasklist_lock);
- stats->version = TASKSTATS_VERSION;
+ unlock_task_sighand(first, &flags);
+ rc = 0;
+out:
+ rcu_read_unlock();
+
+ stats->version = TASKSTATS_VERSION;
/*
* Accounting subsytems can also add calls here to modify
* fields of taskstats.
*/
- put_task_struct(first);
- return 0;
+ return rc;
}