Messages in this thread | | | Date | Thu, 2 Apr 2015 20:08:03 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/3] context_tracking: Inherit TIF_NOHZ through forks instead of context switches |
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On 04/02, Frederic Weisbecker wrote: > > +void context_tracking_cpu_set(int cpu) > { > - clear_tsk_thread_flag(prev, TIF_NOHZ); > - set_tsk_thread_flag(next, TIF_NOHZ); > + static bool initialized = false; > + struct task_struct *p, *t; > + unsigned long flags; > + > + if (!per_cpu(context_tracking.active, cpu)) { > + per_cpu(context_tracking.active, cpu) = true; > + static_key_slow_inc(&context_tracking_enabled); > + } > + > + if (initialized) > + return; > + > + set_tsk_thread_flag(&init_task, TIF_NOHZ); > + > + /* > + * There shouldn't be any thread at this early boot stage > + * but the scheduler is ready to host any. So lets walk > + * the tasklist just in case. tasklist_lock isn't necessary > + * either that early but take it for correctness checkers. > + */ > + read_lock_irqsave(&tasklist_lock, flags); > + for_each_process_thread(p, t) > + set_tsk_thread_flag(t, TIF_NOHZ); > + read_unlock_irqrestore(&tasklist_lock, flags); > + > + initialized = true; > }
Agreed, but _irqsave is not needed. read_lock(tasklist) should work just fine.
Any reason 3/3 comes as a separate change? I won't argue, just curious.
Oleg.
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