From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C1500468C06; Wed, 29 Jul 2026 19:25:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785353152; cv=none; b=l05psSxy3ItNTxvfvrHxe/Km7apUkFl27ZOsHRfk2wr3DmkAXA2VYcXU62H33GIW0BMAinkzUOcRhtV+yWH1TAT0PWkbuKx6uLL211ZYVBdAExybLCZwjEv7s8ynlQgRSwSpNyvT60ecnOJ00zWwmOQYMubNysILcsWH3HQreGw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785353152; c=relaxed/simple; bh=u2sU7+g2++/bp1aHNbYDMDe0dRren1MNlMLqkD+ot74=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=EVe6MuQ9yNHtD3H7oLCILQXzOhYVDZso4Xj8QEFes5CKdG5y3hTVvkvn5IW/MimnJw/n+ob4f2ii7ae6BRB6SIG6XcWnK0Wf3mtnn4pe0VEQ26r6qFge64lM/FxSspeIWbvhjqWWkiG7jEMtP5jj87kOzdBUhMAOJiZ3dd4+gMs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VqSOVLCi; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VqSOVLCi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75B181F000E9; Wed, 29 Jul 2026 19:25:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785353147; bh=FfP6XWvrCgro9QB2TBf6Ep4o2Rb3oAsMZ1Xxvy4f9RY=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=VqSOVLCipMECvYXKqJGXZ2r/x0eBxtxQLwtpnlHSEAeeEDuxGLLKidDJVObfCito+ PUC+7EqnJ7tqPRheIjL7eGiE/vSvc/2zEwnzmqpq456j0/h5Pgol0ZkwWSKLmnUN1t mjRW2DmxmFsiKaeoYzSoUJgM2GmyV9mX4OccdcYMeo7DfiGH0UI/UJLFoStbePAp4C 4JIgbRD2ZMfxU7rtqZt7ZZa3UhghoNLokEFr5amDY7G4ZdHmSQD3De0ITornUJqzGv NXFazA/a632l+KH3Nl0z6pePI5VTslpFudpeDh61feRvH3iyXbeQXtBzPZnEHUy34G qq0BIh4wEvW0Q== Date: Wed, 29 Jul 2026 20:25:43 +0100 From: Jonathan Cameron To: Dave Jiang Cc: linux-cxl@vger.kernel.org, linux-perf-users@vger.kernel.org, will@kernel.org, mark.rutland@arm.com, dave@stgolabs.net, sashiko-bot@kernel.org Subject: Re: [PATCH v2 5/9] perf/cxl: Keep the overflow interrupt pinned to the managed CPU Message-ID: <20260729202543.697b52f3@jic23-huawei> In-Reply-To: <20260729145555.3919550-6-dave.jiang@intel.com> References: <20260729145555.3919550-1-dave.jiang@intel.com> <20260729145555.3919550-6-dave.jiang@intel.com> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 29 Jul 2026 07:55:51 -0700 Dave Jiang wrote: > The PMU pins its overflow interrupt to info->on_cpu in the hotplug > online/offline callbacks, but requests it with only IRQF_SHARED | > IRQF_NO_THREAD. Without IRQF_NOBALANCING, irqbalance or a userspace > smp_affinity write can move the interrupt to another CPU. cxl_pmu_irq() > then runs cxl_pmu_read() there, doing local64_cmpxchg()/local64_add() on > hwc->prev_count and event->count concurrently with the managing CPU; > local64_t is only atomic against same-CPU access, so counts get > corrupted. > > Add IRQF_NOBALANCING so the pinning done in the hotplug callbacks holds, > matching other uncore-style PMU drivers. > > Fixes: 5d7107c72796 ("perf: CXL Performance Monitoring Unit driver") > Reported-by: sashiko-bot@kernel.org > Closes: https://sashiko.dev/#/patchset/20260715191454.459673-1-dave@stgolabs.net?part=1 > Assisted-by: Claude:claude-opus-4-8 > Signed-off-by: Dave Jiang Reviewed-by: Jonathan Cameron > --- > drivers/perf/cxl_pmu.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/perf/cxl_pmu.c b/drivers/perf/cxl_pmu.c > index d1e810601e36..8b89db8f4d68 100644 > --- a/drivers/perf/cxl_pmu.c > +++ b/drivers/perf/cxl_pmu.c > @@ -888,7 +888,8 @@ static int cxl_pmu_probe(struct device *dev) > if (!irq_name) > return -ENOMEM; > > - rc = devm_request_irq(dev, irq, cxl_pmu_irq, IRQF_SHARED | IRQF_NO_THREAD, > + rc = devm_request_irq(dev, irq, cxl_pmu_irq, > + IRQF_SHARED | IRQF_NO_THREAD | IRQF_NOBALANCING, > irq_name, info); > if (rc) > return rc;