From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 12E0A2FC003 for ; Mon, 15 Sep 2025 10:35:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757932512; cv=none; b=O1np4zQmz25LMS58oROGhJerIWVCalhs9RUc7atV7Sp81iv8qPUZHhZ8Jq0UZty5oWj5NGfmnFpzeTMndLVhyHKEww/E25+OVgGGtCpVp9LD8t2qXJTjipZA/aD68Z4Ls7cCUiPjD00INtlk+BPwEE0STzD4ByebI73GA0xaMKw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757932512; c=relaxed/simple; bh=GnPRJr8bD302g1idVWf4TFYMS+bTOr0gFLqD/VElnlA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lwwa3FclbsV18nT5KZBmg2wasWARbJ0dNqXMpAqs0wijRnCzwYLtKonvSJPzzQRwt5adNNPCkD/00JgqEd6CBRpt9i20SOhGFo9NCQ/S46HBrYA+x3lo/cri/poTe8N1Rl49G/qPoNGlEAZ14NQhHJI+F0lCtBqt5nQLWn5LL3c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=uA5pgx7j; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="uA5pgx7j" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=UgxAjeqJy1+oB7bCgdA2gcYmn4AIRVZ9GkWi6fbS6G8=; b=uA5pgx7jxIHyBFy30qLsN861Et FLj7Z8T9JS/hr3Orow3hv8aF9jbHkQ/qBqwU4mAMJbnYqRKuzm75faBzrQwVNH0O62LPllDoEWbon JG9zJTuiHgyRX0Gg9CBlPJxMH5KKf4K7OKRY4BGUc457bFljzQsz/pUR7hhkgR3PzSfoPAvAWgCST tU/cVVOIvEg5nsRN7yTN9pWLFekUABB2W5V5gPaTkVMhwD1zvA1chvKQS4HJbpv1ZCZWqW0+w5ztQ ypMBjcpJD5ldPZBPsnDoF5px/4JLHx1EKPmrhhQ8IlUj9yFTzn8WRxI7QNMH0QAk+puVGlFF7Z3U+ HQ373aNg==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1uy6Y7-0000000D6F7-0mUn; Mon, 15 Sep 2025 10:35:07 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id A7674302E03; Mon, 15 Sep 2025 12:35:06 +0200 (CEST) Date: Mon, 15 Sep 2025 12:35:06 +0200 From: Peter Zijlstra To: Will Deacon Cc: Yunhui Cui , akpm@linux-foundation.org, catalin.marinas@arm.com, maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, kees@kernel.org, masahiroy@kernel.org, aliceryhl@google.com, ojeda@kernel.org, thomas.weissschuh@linutronix.de, xur@google.com, ruanjinjie@huawei.com, gshan@redhat.com, maz@kernel.org, suzuki.poulose@arm.com, zhanjie9@hisilicon.com, yangyicong@hisilicon.com, dianders@chromium.org, gautam@linux.ibm.com, arnd@arndb.de, zhao.xichao@vivo.com, rppt@kernel.org, lihuafei1@huawei.com, coxu@redhat.com, jpoimboe@kernel.org, yaozhenguo1@gmail.com, luogengkun@huaweicloud.com, max.kellermann@ionos.com, tj@kernel.org, wangjinchao600@gmail.com, yury.norov@gmail.com, thorsten.blum@linux.dev, x86@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-perf-users@vger.kernel.org Subject: Re: [PATCH] watchdog: remove HARDLOCKUP_DETECTOR_PERF Message-ID: <20250915103506.GA3245006@noisy.programming.kicks-ass.net> References: <20250915035355.10846-1-cuiyunhui@bytedance.com> 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-Disposition: inline In-Reply-To: On Mon, Sep 15, 2025 at 11:26:09AM +0100, Will Deacon wrote: > | If all CPUs are hard locked up at the same time the buddy system > | can't detect it. > > Ok, so why is that limitation acceptable? It looks to me like you're > removing useful functionality. Yeah, this. I've run into this case waaay too many times to think it reasonable to remove the perf/NMI based lockup detector.