Return-path: Received: from mail-bk0-f50.google.com ([209.85.214.50]:38655 "EHLO mail-bk0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753253Ab3HFG5m convert rfc822-to-8bit (ORCPT ); Tue, 6 Aug 2013 02:57:42 -0400 Received: by mail-bk0-f50.google.com with SMTP id ik8so4534bkc.37 for ; Mon, 05 Aug 2013 23:57:41 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <87iozkf5w0.fsf@kamboji.qca.qualcomm.com> References: <1375430329-23352-1-git-send-email-bartosz.markowski@tieto.com> <87iozkf5w0.fsf@kamboji.qca.qualcomm.com> Date: Tue, 6 Aug 2013 08:57:40 +0200 Message-ID: (sfid-20130806_085745_942393_3DEC7432) Subject: Re: [PATCH v2] ath10k: add SoC power save option to PCI features map From: Michal Kazior To: Kalle Valo Cc: Bartosz Markowski , linux-wireless@vger.kernel.org, ath10k@lists.infradead.org Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 5 August 2013 18:40, Kalle Valo wrote: > Michal Kazior writes: > >> On 2 August 2013 09:58, Bartosz Markowski wrote: >>> Unify the PCI options location. >>> >>> By default the SoC PS option is disabled to boost the >>> performance and due to poor stability on early HW revisions. >>> In future we can remove the module parameter and turn on/off >>> the PS for given hardware. >>> >>> This change also makes the pci module parameter for SoC PS static. >>> >>> Signed-off-by: Bartosz Markowski >> >> Hmm.. I'm worried about pci wake/sleep locking: >> >> (a) pci_wake() (awake count =1) >> (a) do something >> Now, if pci_sleep() and pci_wake() happen simultaneously/are >> preempted splitting primitive operations to: >> (a) pci_sleep(): decrease awake count (=0) >> (b) pci_wake(): increase awake count (=1), iowrite, wait for awake, return >> (a) pci_sleep(): iowrite(). return >> The flow in (b) now thinks the device is awake, but it's not >> guaranteed to be anymore because it has been put to sleep by (a). > > Yeah, there's a race alright. I wonder if I have ever seen a proper use > of a atomic variable in a wireless driver :) > > But this doesn't prevent taking this patch as the race has existed since > the beginning, right? I don't have anything against it. I just noticed the race and thought it's good to point out the issue. Pozdrawiam / Best regards, Michał Kazior.