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Date: Thu, 17 Jan 2013 16:26:02 +0530 From: Preeti U Murthy <preeti@...ux.vnet.ibm.com> To: Ivo Sieben <meltedpianoman@...il.com> CC: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>, Oleg Nesterov <oleg@...hat.com>, Jiri Slaby <jslaby@...e.cz>, Alan Cox <alan@...rguk.ukuu.org.uk>, linux-serial@...r.kernel.org, Alan Cox <alan@...ux.intel.com>, Greg KH <gregkh@...uxfoundation.org> Subject: Re: [PATCH] tty: Only wakeup the line discipline idle queue when queue is active On 01/16/2013 05:32 PM, Ivo Sieben wrote: > 2013/1/16 Preeti U Murthy <preeti@...ux.vnet.ibm.com>: >> >> Yes.Thank you very much for the explanation :) But I dont see how the >> context switching goes away with your patch.With your patch, when the >> higher priority thread comes in when the lower priority thread is >> running in the critical section,it will see the wait queue empty and >> "continue its execution" without now wanting to enter the critical >> section.So this means it will preempt the lower priority thread because >> it is not waiting on a lock anyway.There is a context switch here right? >> I dont see any problem in scheduling due to this,but I do think your >> patch is essential. >> > > I don't have a problem that there is a context switch to the high > priority process: it has a higher priority, so it probably is more > important. > My problem is that even when the waitqueue is empty, the high priority > thread has a risk to block on the spinlock needlessly (causing context > switches to low priority task and back to the high priority task) > Fair enough Ivo.I think you should go ahead with merging the waitqueue_active() wake_up() logic into the wake_up() variants. Regards Preeti U Murthy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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