On Mon, Oct 12, 2015 at 12:03:06PM +0200, Daniel Wagner wrote: > On 10/12/2015 11:17 AM, Daniel Wagner wrote: > > On 09/09/2015 04:26 PM, Peter Zijlstra wrote: > >> On Wed, Sep 09, 2015 at 02:05:29PM +0200, Daniel Wagner wrote: > >>> @@ -50,10 +50,10 @@ void complete_all(struct completion *x) > >>> { > >>> unsigned long flags; > >>> > >>> - spin_lock_irqsave(&x->wait.lock, flags); > >>> + raw_spin_lock_irqsave(&x->wait.lock, flags); > >>> x->done += UINT_MAX/2; > >>> - __wake_up_locked(&x->wait, TASK_NORMAL, 0); > >>> - spin_unlock_irqrestore(&x->wait.lock, flags); > >>> + swake_up_locked(&x->wait); > >>> + raw_spin_unlock_irqrestore(&x->wait.lock, flags); > >>> } > >>> EXPORT_SYMBOL(complete_all); > >> > >> I don't think that's correct; __wake_up_locked(.nr=0) would wake all > >> waiters, where swake_up_locked() will only wake one. > > > > I read that x->done should be protected via wait.lock during the whole > > operation. swake_up_all() will release and reacquire the lock while > > processing the all waiters. So we need to get > > > > Could we play a trick like setting the highest bit in done for > > indicating the complete_all() operation. The UINT_MAX/2 update looks > > like do this by setting a value which has the biggest offset from 0 (but > > why adding instead of just going for assigning...). > > > I had something like this here in mind:
I'm not exactly sure what problem you're trying to solve here.. The fact that we cannot call swake_all() while holding &x->wait.lock, or the fact that complete_all() is typically called from a context which cannot do swake_all() either? Note: Documentation/scheduler/completion.txt:complete() and complete_all() can be called in hard-irq/atomic context safely. Which is very much _NOT_ true of swake_all(). -- 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/