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[204.195.22.127]) by smtp.gmail.com with ESMTPSA id w187sm15863213pfw.62.2019.12.25.12.24.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Dec 2019 12:24:46 -0800 (PST) Date: Wed, 25 Dec 2019 12:24:24 -0800 From: Stephen Hemminger To: Fenghua Yu Cc: David Miller , michael.chan@broadcom.com, netdev@vger.kernel.org, tglx@linutronix.de, luto@kernel.org, peterz@infradead.org, tony.luck@intel.com, David.Laight@ACULAB.COM, ravi.v.shankar@intel.com Subject: Re: [PATCH] drivers/net/b44: Change to non-atomic bit operations Message-ID: <20191225122424.5bc18036@hermes.lan> In-Reply-To: <20191225011020.GE241295@romley-ivt3.sc.intel.com> References: <1576884551-9518-1-git-send-email-fenghua.yu@intel.com> <20191224.161826.37676943451935844.davem@davemloft.net> <20191225011020.GE241295@romley-ivt3.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, 24 Dec 2019 17:10:20 -0800 Fenghua Yu wrote: > On Tue, Dec 24, 2019 at 04:18:26PM -0800, David Miller wrote: > > From: Fenghua Yu > > Date: Fri, 20 Dec 2019 15:29:11 -0800 > > > > > On x86, accessing data across two cache lines in one atomic bit > > > operation (aka split lock) can take over 1000 cycles. > > > > This happens during configuration of WOL, nobody cares that the atomic > > operations done in this function take 1000 cycles each. > > > > I'm not applying this patch. It is gratuitous, and the commit message > > talks about "performance" considuations (cycle counts) that completely > > don't matter here. > > > > If you are merely just arbitrarily trying to remove locked atomic > > operations across the tree for it's own sake, then you should be > > completely honest about that in your commit message. > > We are enabling split lock in the kernel (by default): > https://lkml.org/lkml/2019/12/12/1129 > > After applying the split lock detection patch, the set_bit() in b44.c > may cause split lock and kernel dies. > > So should I change the commit message to add the above info? > > Thanks. > > -Fenghua Why not just make pwol_pattern aligned and choose the right word to do the operation on?