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[2003:ea:8f06:5500:e1db:b990:7e09:f1cf]) by smtp.googlemail.com with ESMTPSA id c4sm5549899wrw.72.2021.01.06.15.18.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 06 Jan 2021 15:18:49 -0800 (PST) To: Andrew Lunn Cc: Russell King - ARM Linux , Jakub Kicinski , David Miller , "netdev@vger.kernel.org" References: From: Heiner Kallweit Subject: Re: [PATCH net-next] net: phy: replace mutex_is_locked with lockdep_assert_held in phylib Message-ID: <17717d40-ff36-dd59-bfaf-0abb513bab06@gmail.com> Date: Thu, 7 Jan 2021 00:18:41 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 06.01.2021 23:39, Andrew Lunn wrote: > On Wed, Jan 06, 2021 at 02:03:40PM +0100, Heiner Kallweit wrote: >> Switch to lockdep_assert_held(_once), similar to what is being done >> in other subsystems. One advantage is that there's zero runtime >> overhead if lockdep support isn't enabled. > > Hi Heiner > Hi Andrew, > I'm not sure we are bothered about performance here. MDIO operations > are slow, a mutex check is fast relative to that. > Right, the performance gain is neglectible here. What I see is that more and more similar checks (e.g. in_softirq, in_irq) are migrated to the lockdep framework. And as stated in the commit message I've seen a number of equivalent patches in other subsystems. > I wonder how many do development work with lockdep enabled? I think i > prefer catching hard to find locking bugs earlier, verses a tiny > performance overhead. > Well, I always develop with lockdep enabled and like the fact that it provides a multitude of checks with minimal overhead. Would be interesting to know the ratio of kernel developers counting on lockdep. > Andrew > Heiner