[PATCH] sys_times: don't take tasklist_lock
Oleg Nesterov [Wed, 29 Mar 2006 00:11:21 +0000 (16:11 -0800)]
sys_times: don't take tasklist_lock

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/sys.c

index 84371fd..7ef7f60 100644 (file)
@@ -1206,7 +1206,7 @@ asmlinkage long sys_times(struct tms __user * tbuf)
                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;
@@ -1216,20 +1216,9 @@ asmlinkage long sys_times(struct tms __user * tbuf)
                        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);