From patchwork Fri Nov 22 03:59:20 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13882750 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EB0D2A31; Fri, 22 Nov 2024 03:59:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732247978; cv=none; b=WhXT226VyA2npeE7QAOkedpusWAiYX77sbnXw4MGQqbJpbiGHAmij/BZZV3Bl/5VjNgNRjk2hvB0v8b9929tnGnItxrpH3Y4FFw69UtKZ3YVMwlvnElw28XgDsgPlv3PXivCZtIM3es/JWhiMAEd4hbkf7eJ5o5q0o0RNdtEuIg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732247978; c=relaxed/simple; bh=OLi4SqzR5SzIfTiMCGYx8+GjgOw02FBSpOAD4lu+xHM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=FUINmdpRg1WmGtSHfPNRfsAMZDYCN95JqZOZInjYIaBUHrPUMvMsXuH/P0k6PRsoTbiw5g96Ex4iaxdRHASQFnS2lh5sNB6AzvcmlQJgC91pKIkHN2YfyzOYM/+412TzzzxhI+YqxrsnjJyhlSRcM2KnP7bVlFS5ttKGYCV2v6E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QteQ7s1o; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QteQ7s1o" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 46D8AC4CECE; Fri, 22 Nov 2024 03:59:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732247977; bh=OLi4SqzR5SzIfTiMCGYx8+GjgOw02FBSpOAD4lu+xHM=; h=From:To:Cc:Subject:Date:From; b=QteQ7s1oRJNNSxaDT28yrtw6ZpTIDCC3Bnz7cwpKqEy47yp7lrHgGUVkrzUHFzTCf yvRZEQlWkXcYX4SjdEzXWsvfM9JmXPGmFO4dn3GN2Rqg3fTQXH9qrFOVA4AytSD66q 4Vm/K7EEQRQl2ME75jZPp5q3P3CJaHXe1VoEz84SCRFPuU41rEwayAKmo4+TouIgA8 JZT6oPYb0ZQE4YJMMuyAtEjjUARRzrT3GsVNIaubiSm4LTjCZGy80V1xEaNlQZY5In RFgqpA7CPI0ampH4G5c4cCAKOfZYjkG2i+sLwonjLAXvUMsFnnpZwA1wlVRexesHmP NhdxKXkqo/d8w== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, peterz@infradead.org, mingo@kernel.org, torvalds@linux-foundation.org Cc: oleg@redhat.com, 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, mjguzik@gmail.com, brauner@kernel.org, jannh@google.com, mhocko@kernel.org, vbabka@suse.cz, shakeel.butt@linux.dev, hannes@cmpxchg.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, david@redhat.com, arnd@arndb.de, viro@zeniv.linux.org.uk, hca@linux.ibm.com, Andrii Nakryiko Subject: [PATCH v5 tip/perf/core 0/2] uprobes: speculative lockless VMA-to-uprobe lookup Date: Thu, 21 Nov 2024 19:59:20 -0800 Message-ID: <20241122035922.3321100-1-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Implement speculative (lockless) resolution of VMA to inode to uprobe, bypassing the need to take mmap_lock for reads, if possible. This series is based on Suren's patch set [2], which adds mm_struct helpers that help detect whether mm_struct was changed, which is used by uprobe logic to validate that speculative results can be trusted after all the lookup logic results in a valid uprobe instance. Patch #1 is a simplification to uprobe VMA flag checking, suggested by Oleg. Patch #2 is the speculative VMA-to-uprobe resolution logic itself, and is the focal point of this patch set. It makes entry uprobes in common case scale very well with number of CPUs, as we avoid any locking or cache line bouncing between CPUs. See corresponding patch for details and benchmarking results. Note, this patch set assumes that FMODE_BACKING files were switched to have SLAB_TYPE_SAFE_BY_RCU semantics, which was recently done by Christian Brauner in [0]. This change can be pulled into perf/core through stable tags/vfs-6.13.for-bpf.file tag from [1]. [0] https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/commit/?h=vfs-6.13.for-bpf.file&id=8b1bc2590af61129b82a189e9dc7c2804c34400e [1] git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git [2] https://lore.kernel.org/linux-mm/20241121162826.987947-1-surenb@google.com/ v4->v5: - rebase on top of Suren's latest version of mm patches addressing Peter's comment and API renaming request; v3->v4: - rebased and dropped data_race(), given mm_struct uses real seqcount (Peter); v2->v3: - dropped kfree_rcu() patch (Christian); - added data_race() annotations for fields of vma and vma->vm_file which could be modified during speculative lookup (Oleg); - fixed int->long problem in stubs for mmap_lock_speculation_{start,end}(), caught by Kernel test robot; v1->v2: - adjusted vma_end_write_all() comment to point out it should never be called manually now, but I wasn't sure how ACQUIRE/RELEASE comments should be reworded (previously requested by Jann), so I'd appreciate some help there (Jann); - int -> long change for mm_lock_seq, as agreed at LPC2024 (Jann, Suren, Liam); - kfree_rcu_mightsleep() for FMODE_BACKING (Suren, Christian); - vm_flags simplification in find_active_uprobe_rcu() and find_active_uprobe_speculative() (Oleg); - guard(rcu)() simplified find_active_uprobe_speculative() implementation. Andrii Nakryiko (2): uprobes: simplify find_active_uprobe_rcu() VMA checks uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution kernel/events/uprobes.c | 47 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 46 insertions(+), 1 deletion(-)