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Subject[PATCH 1/6] sys_times: don't take tasklist_lock
sys_times: dont' take tasklist_lock

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

--- 2.6.16-rc3/kernel/sys.c~ Thu Feb 23 00:27:27 2006
+++ 2.6.16-rc3/kernel/sys.c Thu Feb 23 00:28:24 2006
@@ -1018,7 +1018,7 @@ asmlinkage long sys_times(struct tms __u
struct task_struct *t;
cputime_t utime, stime, cutime, cstime;

- read_lock(&tasklist_lock);
+ spin_lock_irq(&tsk->sighand->siglock);
utime = tsk->signal->utime;
stime = tsk->signal->stime;
t = tsk;
@@ -1028,20 +1028,9 @@ asmlinkage long sys_times(struct tms __u
t = next_thread(t);
} while (t != tsk);

- /*
- * While we have tasklist_lock read-locked, no dying thread
- * can be updating current->signal->[us]time. Instead,
- * we got their counts included in the live thread loop.
- * However, another thread can come in right now and
- * do a wait call that updates current->signal->c[us]time.
- * To make sure we always see that pair updated atomically,
- * we take the siglock around fetching them.
- */
- spin_lock_irq(&tsk->sighand->siglock);
cutime = tsk->signal->cutime;
cstime = tsk->signal->cstime;
spin_unlock_irq(&tsk->sighand->siglock);
- read_unlock(&tasklist_lock);

tmp.tms_utime = cputime_to_clock_t(utime);
tmp.tms_stime = cputime_to_clock_t(stime);
-
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