Return-path: Received: from mx2.uni-rostock.de ([139.30.22.72]:50673 "EHLO mx1.uni-rostock.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753528AbeAZPxn (ORCPT ); Fri, 26 Jan 2018 10:53:43 -0500 Subject: Re: [PATCH v2] mac80211_hwsim: don't use WQ_MEM_RECLAIM To: Tejun Heo , Johannes Berg CC: Arend van Spriel , linux-wireless References: <20180124074051.19939-1-johannes@sipsolutions.net> <7eb10bf1-7825-3dae-b813-d912e6670440@uni-rostock.de> <1516790786.2508.43.camel@sipsolutions.net> <5A6A3BFC.5090305@broadcom.com> <1516914086.2189.9.camel@sipsolutions.net> <20180125222650.GJ17457@devbig577.frc2.facebook.com> <1516954082.2189.14.camel@sipsolutions.net> <20180126150530.GK17457@devbig577.frc2.facebook.com> From: Benjamin Beichler Message-ID: (sfid-20180126_165528_159561_8D490F7D) Date: Fri, 26 Jan 2018 16:53:37 +0100 MIME-Version: 1.0 In-Reply-To: <20180126150530.GK17457@devbig577.frc2.facebook.com> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="------------ms000801010008030800010103" Sender: linux-wireless-owner@vger.kernel.org List-ID: --------------ms000801010008030800010103 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: de-DE Hi, Am 26.01.2018 um 16:05 schrieb Tejun Heo: > Hello, > > On Fri, Jan 26, 2018 at 09:08:02AM +0100, Johannes Berg wrote: >> Not that you mention it ... Honestly though, wifi connections break al= l >> the time, so not sure you'd really want that. But anyway, that's what >> we have. > I'd be a lot happier to remove WQ_MEM_RECLAIM from wireless drivers > too, and glancing the code, it looked like there already are so many > holes that whether having that flag or not shouldn't matter all that > much. It was just difficult for me to make a case for removing it > preemptively. If you're up for it, please be my guest. I think, it is quite clear, why this error is produced, since in memory reclaim, we should not synchronously flush unimportant work queues. I think there could be valid use cases to have work queues with that flag in wireless drivers, if the are used carefully. Therefore I suggest a hint in the work queue documentation like: "Check whether work_items on WQ_MEM_RECLAIM wq may actively delay memory reclaim with network timeouts and check whether other work queues without WQ_MEM_RECLAIM may be flushed within work_items of the queue, as this will prioritize non-reclaiming work_items on the flushed queue the same level as reclaiming work_items". At least this can help for future usage, as it could have avoided my error :-D > Thanks. > --=20 M.Sc. Benjamin Beichler Universit=C3=A4t Rostock, Fakult=C3=A4t f=C3=BCr Informatik und Elektrote= chnik Institut f=C3=BCr Angewandte Mikroelektronik und Datentechnik University of Rostock, Department of CS and EE Institute of Applied Microelectronics and CE Richard-Wagner-Stra=C3=9Fe 31 18119 Rostock Deutschland/Germany phone: +49 (0) 381 498 - 7278 email: Benjamin.Beichler@uni-rostock.de www: http://www.imd.uni-rostock.de/ --------------ms000801010008030800010103 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCC D/kwggTVMIIDvaADAgECAghQTsb1PRG0ZDANBgkqhkiG9w0BAQsFADBxMQswCQYDVQQGEwJE RTEcMBoGA1UEChMTRGV1dHNjaGUgVGVsZWtvbSBBRzEfMB0GA1UECxMWVC1UZWxlU2VjIFRy dXN0IENlbnRlcjEjMCEGA1UEAxMaRGV1dHNjaGUgVGVsZWtvbSBSb290IENBIDIwHhcNMTQw 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