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Wed, 16 Apr 2025 01:05:20 -0700 (PDT) Received: from localhost ([122.172.83.32]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-73bd230dd17sm9721455b3a.129.2025.04.16.01.05.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Apr 2025 01:05:19 -0700 (PDT) Date: Wed, 16 Apr 2025 13:35:17 +0530 From: Viresh Kumar To: Chun-Jen Tseng =?utf-8?B?KOabvuS/iuS7gSk=?= Cc: "cw00.choi@samsung.com" , "rafael@kernel.org" , Project_Global_Chrome_Upstream_Group , AngeloGioacchino Del Regno , "myungjoo.ham@samsung.com" , "linux-kernel@vger.kernel.org" , "kyungmin.park@samsung.com" , "linux-arm-kernel@lists.infradead.org" , "matthias.bgg@gmail.com" , "linux-pm@vger.kernel.org" , "linux-mediatek@lists.infradead.org" Subject: Re: [PATCH v3 1/3] cpufreq: mediatek: using global lock avoid race condition Message-ID: <20250416080517.feansrkpycsynk6t@vireshk-i7> References: <20250214074353.1169864-1-chun-jen.tseng@mediatek.com> <20250214074353.1169864-2-chun-jen.tseng@mediatek.com> <20250219054209.erwfp7sgzchaiuds@vireshk-i7> <20250321045624.mwm2mnkqeow5uids@vireshk-i7> <2a73b5ca35692c8ffa68c9ff0df73e24a592967d.camel@mediatek.com> <20250321060148.adhxjexpnm4dkpnt@vireshk-i7> <20250324054333.sgwwksawnybx3lp4@vireshk-i7> <06356a55cdb3c34dfc716349d1967f95655b0ab2.camel@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <06356a55cdb3c34dfc716349d1967f95655b0ab2.camel@mediatek.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250416_010520_853683_521DB750 X-CRM114-Status: GOOD ( 12.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 14-04-25, 08:42, Chun-Jen Tseng (曾俊仁) wrote: > Hi Viresh, > > The CCI level choose by Max_Level(LCPU & BCPU frequency) in devfreq > driver. > without global lock, It may choose wrong CCI level and cause system > stall. > > I hope this flow is serial setting like, BCPU / LCPU set frequency -> > set CCI level -> BCPU / LCPU set frequency -> set CCI level -> ...... > > without global lock, it could be LCPU / BCPU set frequency -> set CCI > level(during this time, it may change BCPU / LCPU frequency and cause > system stall. > > I also can only do global lock on ccifreq_support SoC. As explained earlier, I don't think there is a race here. May be I am wrong. And so I need a clear code path example from you, which proves that there is a race here. -- viresh