On 08/14, Oleg Nesterov wrote: > > OK, lets forget about alternative approach for now. We can reconsider > it later. At least I have to admit that seqlock is more straighforward.
Yes. But just for record, the "lockless" version doesn't look that bad to me, void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times) { struct signal_struct *sig = tsk->signal; bool lockless, is_dead; struct task_struct *t; unsigned long flags; u64 exec; lockless = true; is_dead = !lock_task_sighand(p, &flags); retry: times->utime = sig->utime; times->stime = sig->stime; times->sum_exec_runtime = exec = sig->sum_sched_runtime; if (is_dead) return; if (lockless) unlock_task_sighand(p, &flags); rcu_read_lock(); for_each_thread(tsk, t) { cputime_t utime, stime; task_cputime(t, &utime, &stime); times->utime += utime; times->stime += stime; times->sum_exec_runtime += task_sched_runtime(t); } rcu_read_unlock(); if (lockless) { lockless = false; is_dead = !lock_task_sighand(p, &flags); if (is_dead || exec != sig->sum_sched_runtime) goto retry; } unlock_task_sighand(p, &flags); } The obvious problem is that we should shift lock_task_sighand() from the callers to thread_group_cputime() first, or add thread_group_cputime_lockless() and change the current users one by one. And of course, stats_lock is more generic. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/