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Wed, 5 Oct 2022 21:10:35 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6500,9779,10491"; a="304267650" X-IronPort-AV: E=Sophos;i="5.95,161,1661842800"; d="scan'208";a="304267650" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Oct 2022 14:10:34 -0700 X-IronPort-AV: E=McAfee;i="6500,9779,10491"; a="626750208" X-IronPort-AV: E=Sophos;i="5.95,161,1661842800"; d="scan'208";a="626750208" Received: from vcostago-desk1.jf.intel.com (HELO vcostago-desk1) ([10.54.70.10]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Oct 2022 14:10:33 -0700 From: Vinicius Costa Gomes To: "Kolacinski, Karol" , "Nguyen, Anthony L" , "intel-wired-lan@lists.osuosl.org" In-Reply-To: References: <20221003095519.539390-1-karol.kolacinski@intel.com> <20221003095519.539390-2-karol.kolacinski@intel.com> <7b4176bc-a5a8-467f-f2f2-a7defb37b89f@intel.com> Date: Wed, 05 Oct 2022 14:10:33 -0700 Message-ID: <87bkqqou2e.fsf@intel.com> MIME-Version: 1.0 X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1665004236; x=1696540236; h=from:to:subject:in-reply-to:references:date:message-id: mime-version; bh=kG12J6bHIPnLR/2CRKT2dSoe1vaH3Osy1bCl4nHehpo=; b=QqH1gz+foRSuqEyPRaGSnxH4L3duIAlYX1kny2e+ASwvV1IAS6yQyVmO DnYhERoVdwJewl+eQ1LEaxEVBCwbea2yK1f4GKVitBLtE0Kvz5mU41ywB WnvBN19O/KDhC8Fm3CQRpObM96EAYxWZ3Q9U861JGrv/nGKNC63wpOrq2 +croFKSeOGo4RgFdgD9EJVxb6r7it3beEoVRo5uyZPitHe2XxPNAsfU84 1cRCC4+Ua1CVp/z2S8dfR/Ax23eUVsxBzlanh3HmVrnoqCWmRpEr5mwcN s9KEK6afph+rPO6jK7Ej53HR+yiOZRlXGG9mEnVP3+ZNyVJDFPLZuqGVj g==; X-Mailman-Original-Authentication-Results: smtp3.osuosl.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=QqH1gz+f Subject: Re: [Intel-wired-lan] [PATCH net-next 2/2] ice: Remove gettime HW semaphore X-BeenThere: intel-wired-lan@osuosl.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Wired Ethernet Linux Kernel Driver Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-wired-lan-bounces@osuosl.org Sender: "Intel-wired-lan" "Kolacinski, Karol" writes: > Hi Vinicius, > >> I think the problem is less about concurrent writes/reads than >> concurrent reads: the fact that the registers are latched when the >> "lower" register is read, makes me worried that there's a (very narrow) >> window during rollover in which the "losing" read (of multiple threads >> doing reads) can return a wrong value. > > The issue in this case is, it's either risk of reading slightly wrong > value or having multiple timeouts and errors. > We experienced a lot of simultaneous reads on multiple PFs (especially > on E822 HW with 8 ports) and even with increased timeout to acquire > the HW semaphore, it still failed. I am wondering if using a hw semaphore is making the problem worse than it needs to be. Why a kernel spinlock can't be used? Cheers, -- Vinicius _______________________________________________ Intel-wired-lan mailing list Intel-wired-lan@osuosl.org https://lists.osuosl.org/mailman/listinfo/intel-wired-lan