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Tue, 09 Jun 2020 15:37:19 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 80F95C4339C; Tue, 9 Jun 2020 15:37:18 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: saiprakash.ranjan) by smtp.codeaurora.org (Postfix) with ESMTPSA id BA605C433CB; Tue, 9 Jun 2020 15:37:16 +0000 (UTC) MIME-Version: 1.0 Date: Tue, 09 Jun 2020 21:07:16 +0530 From: Sai Prakash Ranjan To: Mathieu Poirier Subject: Re: [PATCH 2/2] coresight: tmc: Add shutdown callback for TMC ETR/ETF In-Reply-To: References: <28123d1e19f235f97555ee36a5ed8b52d20cbdea.1590947174.git.saiprakash.ranjan@codeaurora.org> <20200601212858.GB24287@xps15> <6d759cc28628ea72767c1304883630eb@codeaurora.org> <4a09cd2e054836d85f2e024ca4435e91@codeaurora.org> <1a5a6a6d-b86d-df45-cf91-7081e70d88a3@arm.com> <20200603174426.GA23165@xps15> Message-ID: <2776eeee4532b0b84459da169c050ad7@codeaurora.org> X-Sender: saiprakash.ranjan@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200609_083740_056262_E37C2C5F X-CRM114-Status: GOOD ( 16.22 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Will Deacon , Suzuki K Poulose , linux-arm-msm , Coresight ML , Linux Kernel Mailing List , Stephen Boyd , Robin Murphy , linux-arm-kernel , Mike Leach Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Mathieu, On 2020-06-09 20:57, Mathieu Poirier wrote: > On Mon, 8 Jun 2020 at 08:07, Sai Prakash Ranjan > wrote: >> >> Hi Mathieu, Mike >> >> On 2020-06-04 12:57, Sai Prakash Ranjan wrote: >> > >> >> [...] >> >> >> >> >> Robin has a point - user space is long gone at this time. As such the >> >> first >> >> question to ask is what kind of CS session was running at the time the >> >> system >> >> was shutting down. Was it a perf session of a sysfs session? >> >> >> >> I'm guessing it was a sysfs session because user space has been blown >> >> away a >> >> while back and part of that process should have killed all perf >> >> sessions. >> > >> > I was enabling trace via sysfs. >> > >> >> >> >> If I am correct then simply switching off the ETR HW in the shutdown() >> >> amba bus >> >> callback should be fine - otherwise Mike's approach is mandatory. >> >> There is >> >> also the exchange between Robin and Sai about removing the SMMU >> >> shutdown >> >> callback, but that thread is still incomplete. >> >> >> > >> > If Robin is hinting at removing SMMU shutdown callback, then I think >> > adding >> > all these shutdown callbacks to all clients of SMMU can be avoided. Git >> > blaming >> > the thing shows it was added to avoid some kexec memory corruption. >> > >> >> I think I misread the cryptic hint from Robin and it is not right to >> remove >> SMMU shutdown callback. For more details on why that was a bad idea >> and >> would >> break kexec, please refer to [1]. >> >> As for the coresight, can I disable the ETR only in the tmc shutdown >> callback >> or are we still concerned about the userspace coming into picture? > > User space isn't a concern, especially after you've confirmed the > problem occured during an ongoing sysfs session. > Will post v3 with comments addressed after 5.8-rc1 is out. Thanks, Sai -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel