From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5C549D19502 for ; Mon, 26 Jan 2026 18:55:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9C8646B0005; Mon, 26 Jan 2026 13:55:21 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 94C1D6B0089; Mon, 26 Jan 2026 13:55:21 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 824796B008A; Mon, 26 Jan 2026 13:55:21 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 7168E6B0005 for ; Mon, 26 Jan 2026 13:55:21 -0500 (EST) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 18D5713BB23 for ; Mon, 26 Jan 2026 18:55:21 +0000 (UTC) X-FDA: 84375018042.25.CEDEBC3 Received: from 013.lax.mailroute.net (013.lax.mailroute.net [199.89.1.16]) by imf07.hostedemail.com (Postfix) with ESMTP id 1095A40007 for ; Mon, 26 Jan 2026 18:55:18 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=acm.org header.s=mr01 header.b=4b+R0ix5; spf=pass (imf07.hostedemail.com: domain of bvanassche@acm.org designates 199.89.1.16 as permitted sender) smtp.mailfrom=bvanassche@acm.org; dmarc=pass (policy=reject) header.from=acm.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1769453719; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=lrmRnMiS7e8oDqS8sJHadbKNaRE4y8/9HerN9jURAnw=; b=FgYJwnAw5hYylGEmrV7KmhNAI/UnvhYycZWIQ5UQcK/I6O+nJvwkSHsY63v7RdXROVTdtY gFOvhCaEH/aR9pKw/OySoaMCLo4EXQxbrI6G/zZvuOoQmLEE9EORnWZAvs5wL93kJzIQl2 Ou198uPdFURiqL4a4DNqjUsjzufHTKE= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=acm.org header.s=mr01 header.b=4b+R0ix5; spf=pass (imf07.hostedemail.com: domain of bvanassche@acm.org designates 199.89.1.16 as permitted sender) smtp.mailfrom=bvanassche@acm.org; dmarc=pass (policy=reject) header.from=acm.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1769453719; a=rsa-sha256; cv=none; b=SnERUcSR0gVl6e8R6qQX8vA13ju/IJeGwyHDlB/NLbLqkzlv8+EBAh6mshVhIo7UiuhVna Vrajxi5bMjLw68W7AjBiCsOp25tXDyl1JAb8bluWvEQwfY9L/S/3DM8Q6yfzYoWNq1l4+p KDbfkAgFl1yjOamik1qI4jR99jJ8aRU= Received: from localhost (localhost [127.0.0.1]) by 013.lax.mailroute.net (Postfix) with ESMTP id 4f0Hm56kBhzlgyGr; Mon, 26 Jan 2026 18:55:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=acm.org; h= content-transfer-encoding:content-type:content-type:in-reply-to :from:from:content-language:references:subject:subject :user-agent:mime-version:date:date:message-id:received:received; s=mr01; t=1769453709; x=1772045710; bh=lrmRnMiS7e8oDqS8sJHadbKN aRE4y8/9HerN9jURAnw=; b=4b+R0ix5+Os0UdymHVdPefR75pAjuePHzZSBDv1T PhKFA4FAC8OQc9TuXgMxSrv6ALYLM26zsK043txlRzxnGUh1OQAsqSN0foShyawt pgoA82i8a3e56Az+c5yQ/FRzJRlVVV9ONPOmo5QZvE0Q0R6BZlDabDdSvqRaIrWq 5qv/o/SAv+5/3fRLam45SzREjjV6pc62GFn6nBiQJg3JMywlrNKvmQ7VlMyrTxAH T23+3S/pU978iX4yw8ahY2EFo/8Xq0lczgH+hEk7oD3ExiVmcFff0tai2SlH7PR7 9U/uiA5vPsPPUdDSnrYljSKcp1+NnDZMaTuY+V/YB+pCTQ== X-Virus-Scanned: by MailRoute Received: from 013.lax.mailroute.net ([127.0.0.1]) by localhost (013.lax [127.0.0.1]) (mroute_mailscanner, port 10029) with LMTP id vhOvcRL97NLm; Mon, 26 Jan 2026 18:55:09 +0000 (UTC) Received: from [100.119.48.131] (unknown [104.135.180.219]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bvanassche@acm.org) by 013.lax.mailroute.net (Postfix) with ESMTPSA id 4f0Hlj4MJNzlh1T6; Mon, 26 Jan 2026 18:54:57 +0000 (UTC) Message-ID: <8c1bbab4-4615-4518-b773-a006d1402b8b@acm.org> Date: Mon, 26 Jan 2026 10:54:56 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 15/36] srcu: Support Clang's context analysis To: Marco Elver Cc: Peter Zijlstra , Boqun Feng , Ingo Molnar , Will Deacon , "David S. Miller" , Luc Van Oostenryck , Chris Li , "Paul E. McKenney" , Alexander Potapenko , Arnd Bergmann , Christoph Hellwig , Dmitry Vyukov , Eric Dumazet , Frederic Weisbecker , Greg Kroah-Hartman , Herbert Xu , Ian Rogers , Jann Horn , Joel Fernandes , Johannes Berg , Jonathan Corbet , Josh Triplett , Justin Stitt , Kees Cook , Kentaro Takeda , Lukas Bulwahn , Mark Rutland , Mathieu Desnoyers , Miguel Ojeda , Nathan Chancellor , Neeraj Upadhyay , Nick Desaulniers , Steven Rostedt , Tetsuo Handa , Thomas Gleixner , Thomas Graf , Uladzislau Rezki , Waiman Long , kasan-dev@googlegroups.com, linux-crypto@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, linux-sparse@vger.kernel.org, linux-wireless@vger.kernel.org, llvm@lists.linux.dev, rcu@vger.kernel.org References: <20251219154418.3592607-1-elver@google.com> <20251219154418.3592607-16-elver@google.com> Content-Language: en-US From: Bart Van Assche In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: bepzuhoz3karkiwpa6uzeew43pbgb7uz X-Rspamd-Queue-Id: 1095A40007 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1769453718-502169 X-HE-Meta: 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 XjORCCSG iTNc0PoEL5o6Njz2IaaOiBsBVBBSQJNzZmhqc/Rw0chBFBxVMjlE1lsIEOGbR+hX2RpibjD+d0Bx8l9fdPnFYgnoWHUKAbhBMpXLbxIuxZLFVX+ahTJ6WIZa1z+sabMe0kmRYm7rFp0tjGIiZn+HQkBtaDtKkb3BPMVVQtauB6yDnDD36Kyy24dtEcdE8dhcbrisdbaOD00SdNxsePrKkE+GsdcTYxuipQzIXxFbF9ac/wpCs0kSnsR2cPin632EFSNb848abRKOIgVxLh/zfcMzmVygvHr+9Fs417MpfZ4DIaxjK7T85sm7tsv60ZwCYwoUJSP8QIJTZVsRTu/DrHRexiQIE9XDzmqbCxnjCgD145wQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 1/26/26 10:35 AM, Marco Elver wrote: > That being said, I don't think it's wrong to write e.g.: > > spin_lock(&updater_lock); > __acquire_shared(ssp); > ... > // writes happen through rcu_assign_pointer() > // reads can happen through srcu_dereference_check() > ... > __release_shared(ssp); > spin_unlock(&updater_lock); > > , given holding the updater lock implies reader access. > > And given the analysis is opt-in (CONTEXT_ANALYSIS := y), I think > it's a manageable problem. I'd like to make context-analysis mandatory for the entire kernel tree. > If you have a different idea how we can solve this, please let us know. > > One final note, usage of srcu_dereference_check() is rare enough: > > arch/x86/kvm/hyperv.c: irq_rt = srcu_dereference_check(kvm->irq_routing, &kvm->irq_srcu, > arch/x86/kvm/x86.c: kvm_free_msr_filter(srcu_dereference_check(kvm->arch.msr_filter, &kvm->srcu, 1)); > arch/x86/kvm/x86.c: kfree(srcu_dereference_check(kvm->arch.pmu_event_filter, &kvm->srcu, 1)); > drivers/gpio/gpiolib.c: label = srcu_dereference_check(desc->label, &desc->gdev->desc_srcu, > drivers/hv/mshv_irq.c: girq_tbl = srcu_dereference_check(partition->pt_girq_tbl, > drivers/hwtracing/stm/core.c: link = srcu_dereference_check(src->link, &stm_source_srcu, 1); > drivers/infiniband/hw/hfi1/user_sdma.c: pq = srcu_dereference_check(fd->pq, &fd->pq_srcu, > fs/quota/dquot.c: struct dquot *dquot = srcu_dereference_check( > fs/quota/dquot.c: struct dquot *dquot = srcu_dereference_check( > fs/quota/dquot.c: put[cnt] = srcu_dereference_check(dquots[cnt], &dquot_srcu, > fs/quota/dquot.c: transfer_from[cnt] = srcu_dereference_check(dquots[cnt], > include/linux/kvm_host.h: return srcu_dereference_check(kvm->memslots[as_id], &kvm->srcu, > virt/kvm/irqchip.c: irq_rt = srcu_dereference_check(kvm->irq_routing, &kvm->irq_srcu, > > , that I think it's easy enough to annotate these places with the above > suggestions in case you're trying out global enablement. Has it ever been considered to add support in the clang compiler for a variant of __must_hold() that expresses that one of two capabilities must be held by the caller? I think that would remove the need to annotate SRCU update-side code with __acquire_shared(ssp) and __release_shared(ssp). Thanks, Bart.