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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hkVI7-0003Q1-KG; Mon, 08 Jul 2019 15:10:55 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hkVI4-0003PX-MV for linux-arm-kernel@lists.infradead.org; Mon, 08 Jul 2019 15:10:54 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B65E22B; Mon, 8 Jul 2019 08:10:49 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 452853F59C; Mon, 8 Jul 2019 08:10:48 -0700 (PDT) Date: Mon, 8 Jul 2019 16:10:46 +0100 From: Mark Rutland To: Julien Thierry Subject: Re: [PATCH v3 4/9] arm: perf: Remove Remove PMU locking Message-ID: <20190708151045.GF33099@lakrids.cambridge.arm.com> References: <1562596377-33196-1-git-send-email-julien.thierry@arm.com> <1562596377-33196-5-git-send-email-julien.thierry@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1562596377-33196-5-git-send-email-julien.thierry@arm.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190708_081052_777096_1AC7D608 X-CRM114-Status: GOOD ( 15.63 ) 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: peterz@infradead.org, liwei391@huawei.com, will.deacon@arm.com, Russell King , acme@kernel.org, alexander.shishkin@linux.intel.com, mingo@redhat.com, namhyung@kernel.org, jolsa@redhat.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jul 08, 2019 at 03:32:52PM +0100, Julien Thierry wrote: > Since the PMU interrupt saves and restores the value of the selector > register, there is no need to serialize register accesses against the > interrupt contexts. > > For operations that can be called with interrupts enabled, preemption > still needs to be disabled to ensure the programming of the PMU is > done on the expected CPU and not migrated mid-programming. > > Signed-off-by: Julien Thierry > Cc: Will Deacon > Cc: Mark Rutland > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Arnaldo Carvalho de Melo > Cc: Alexander Shishkin > Cc: Jiri Olsa > Cc: Namhyung Kim > Cc: Russell King > --- > arch/arm/kernel/perf_event_v7.c | 56 +++-------------------------------------- > 1 file changed, 4 insertions(+), 52 deletions(-) > static void armv7pmu_start(struct arm_pmu *cpu_pmu) > { > - unsigned long flags; > - struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events); > - > - raw_spin_lock_irqsave(&events->pmu_lock, flags); > + preempt_disable(); > /* Enable all counters */ > armv7_pmnc_write(armv7_pmnc_read() | ARMV7_PMNC_E); > - raw_spin_unlock_irqrestore(&events->pmu_lock, flags); > + preempt_enable(); > } > > static void armv7pmu_stop(struct arm_pmu *cpu_pmu) > { > - unsigned long flags; > - struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events); > - > - raw_spin_lock_irqsave(&events->pmu_lock, flags); > + preempt_disable(); > /* Disable all counters */ > armv7_pmnc_write(armv7_pmnc_read() & ~ARMV7_PMNC_E); > - raw_spin_unlock_irqrestore(&events->pmu_lock, flags); > + preempt_enable(); > } As with the arm64 patch, I suspect/hope it's not necessary to disable preemption here. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel