thread_group_cputime: kill the bogus ->signal != NULL check

Impact: simplify the code

thread_group_cputime() is called by current when it must have the valid
->signal, or under ->siglock, or under tasklist_lock after the ->signal
check, or the caller is wait_task_zombie() which reaps the child. In any
case ->signal can't be NULL.

But the point of this patch is not optimization. If it is possible to call
thread_group_cputime() when ->signal == NULL we are doing something wrong,
and we should not mask the problem. thread_group_cputime() fills *times
and the caller will use it, if we silently use task_struct->*times* we
report the wrong values.

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

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 895337b..3f4377e 100644 (file)
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -58,21 +58,21 @@ void thread_group_cputime(
        struct task_struct *tsk,
        struct task_cputime *times)
 {
-       struct signal_struct *sig;
+       struct task_cputime *totals, *tot;
        int i;
-       struct task_cputime *tot;
 
-       sig = tsk->signal;
-       if (unlikely(!sig) || !sig->cputime.totals) {
+       totals = tsk->signal->cputime.totals;
+       if (!totals) {
                times->utime = tsk->utime;
                times->stime = tsk->stime;
                times->sum_exec_runtime = tsk->se.sum_exec_runtime;
                return;
        }
+
        times->stime = times->utime = cputime_zero;
        times->sum_exec_runtime = 0;
        for_each_possible_cpu(i) {
-               tot = per_cpu_ptr(tsk->signal->cputime.totals, i);
+               tot = per_cpu_ptr(totals, i);
                times->utime = cputime_add(times->utime, tot->utime);
                times->stime = cputime_add(times->stime, tot->stime);
                times->sum_exec_runtime += tot->sum_exec_runtime;