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Thu, 03 Oct 2024 05:32:55 -0400 X-MC-Unique: AvGNL3lSNh-7JtYkcul2nw-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B49581955D56; Thu, 3 Oct 2024 09:32:51 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.226.1]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 801F519560A2; Thu, 3 Oct 2024 09:32:44 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 3 Oct 2024 11:32:37 +0200 (CEST) Date: Thu, 3 Oct 2024 11:32:29 +0200 From: Oleg Nesterov To: Andrii Nakryiko Cc: Andrii Nakryiko , linux-trace-kernel@vger.kernel.org, peterz@infradead.org, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, willy@infradead.org, surenb@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, mjguzik@gmail.com, brauner@kernel.org, jannh@google.com, mhocko@kernel.org, vbabka@suse.cz, mingo@kernel.org Subject: Re: [PATCH v2 tip/perf/core 5/5] uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution Message-ID: <20241003093228.GA20733@redhat.com> References: <20241001225207.2215639-1-andrii@kernel.org> <20241001225207.2215639-6-andrii@kernel.org> <20241002072522.GB27552@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 688CF4000D X-Stat-Signature: hib7gc5k617bh14qfygdtqkxhjx1haak X-HE-Tag: 1727947981-634864 X-HE-Meta: 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 ewMUt1P3 8xa+lhOxFMYCBJ2xVBulOmdbobgeHE7wCKfSKe8D7klLDe8C2069NQay8TX2ST6VGX7FzhOQ0o+hb8nfnXF8qQMwEAVXOOABsFeavG8eIqQsnf3uDRnYD5w3AaWdUvDgUVPbdf3AHjhMMQJ1g3ggLQja/mkPKcfGRTA1f3pU/QslWzM00sXYJlWDSJ1zuYHUTaSljjXmaej2RJhhMhEyXjAy4wRnQ2dx7y2JzLE3eSG589axi8sVjKa5B81Zj9xGvdKGO8nyUtQoQZUq9nKDPQkRfZo4slcBR3EM1xThzAY5BoKg5wLMbHPhNpohVVwuhwD7wx+TMkuHqPxK0vrPTpzHTsSh+qi9gQSoRj6o3Vyq96jVdbM8XiynJatOAeXaXdNg5BpOF/kAVLd+BammeNVJZOb6m0jvlUqSSAT+PLv1aRFg= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000020, 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 10/02, Andrii Nakryiko wrote: > > On Wed, Oct 2, 2024 at 12:25 AM Oleg Nesterov wrote: > > > > > + vm_file = READ_ONCE(vma->vm_file); > > > + if (!vm_file) > > > + return NULL; > > > + > > > + offset = (loff_t)(vma->vm_pgoff << PAGE_SHIFT) + (bp_vaddr - vma->vm_start); > > > > LGTM. But perhaps vma->vm_pgoff and vma->vm_start need READ_ONCE() as well, > > if nothing else to shut up KCSAN if this code races with, say, __split_vma() ? > > We keep going back and forth between reading directly, using > READ_ONCE(), and annotating with data_race(). I don't think it matters > in terms of correctness or performance, so I'm happy to add whatever > incantations that will make everyone satisfied. Let's see what others > think, and I'll incorporate that into the next revision. OK, agreed... And I guess I was wrong anyway, READ_ONCE() alone won't shutup KCSAN in this case. Oleg.