Messages in this thread | | | Date | Thu, 3 Jan 2013 10:49:44 +0100 | Subject | Re: [PATCH] tty: Only wakeup the line discipline idle queue when queue is active | From | Ivo Sieben <> |
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Oleg, Peter, Ingo, Andi & Preeti,
2013/1/2 Jiri Slaby <jslaby@suse.cz>: > On 01/02/2013 04:21 PM, Ivo Sieben wrote: >> I don't understand your responses: do you suggest to implement this >> "if active" behavior in: >> * A new wake_up function called wake_up_if_active() that is part of >> the waitqueue layer? > > Sounds good. > > -- > js > suse labs
I want to ask you 'scheduler' people for your opinion:
Maybe you remember my previous patch where I suggested an extra 'waitqueue empty' check before entering the critical section of the wakeup() function (If you do not remember see https://lkml.org/lkml/2012/10/25/159)
Finally Oleg responded that a lot of callers do
if (waitqueue_active(q)) wake_up(...);
what made my patch pointless and adds a memory barrier. I then decided to also implement the 'waitqueue_active' approach for my problem.
But now I get a review comment by Jiri that he would like to hide this 'if active behavior' in a wake_up_if_active() kind of function. I think he is right that implementing this check in the wakeup function would clean things up, right?
I would like to have your opinion on the following two suggestions: - We still can do the original patch on the wake_up() that I suggested. I then can do an additional code cleanup patch that removes the double 'waitqueue_active' call (a quick grep found about 150 of these waitqueue active calls) on several places in the code. - Or - as an alternative - I could add extra _if_active() versions of all wake_up() functions, that implement this extra test.
Regards, Ivo
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