thread_group_cputime: move a couple of callsites outside of ->siglock
Oleg Nesterov [Mon, 17 Nov 2008 14:40:08 +0000 (15:40 +0100)]
Impact: relax the locking of cpu-time accounting calls

->siglock buys nothing for thread_group_cputime() in do_sys_times() and
wait_task_zombie() (which btw takes the unrelated parent's ->siglock).

Actually I think do_sys_times() doesn't need ->siglock at all.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/exit.c
kernel/sys.c

index ae2b92b..b9c4d8b 100644 (file)
@@ -1330,10 +1330,10 @@ static int wait_task_zombie(struct task_struct *p, int options,
                 * group, which consolidates times for all threads in the
                 * group including the group leader.
                 */
+               thread_group_cputime(p, &cputime);
                spin_lock_irq(&p->parent->sighand->siglock);
                psig = p->parent->signal;
                sig = p->signal;
-               thread_group_cputime(p, &cputime);
                psig->cutime =
                        cputime_add(psig->cutime,
                        cputime_add(cputime.utime,
index 31deba8..5fc3a0c 100644 (file)
@@ -858,8 +858,8 @@ void do_sys_times(struct tms *tms)
        struct task_cputime cputime;
        cputime_t cutime, cstime;
 
-       spin_lock_irq(&current->sighand->siglock);
        thread_group_cputime(current, &cputime);
+       spin_lock_irq(&current->sighand->siglock);
        cutime = current->signal->cutime;
        cstime = current->signal->cstime;
        spin_unlock_irq(&current->sighand->siglock);