From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792635311; b=zAHdkSXMeCfmQmfp4DjLpVTTdAnlVqNZ3R/MSUDj7LMjDynHIUMTSCGfS8Dvj4BzW08u aXSMeeKxT2OAIDW/bHSdCXzu+Yu2k2iqU3TKtbpefLyugaxcRnEt8kdrRPkVeMrvP3Axv 7RIgJSmoVxTjaFYewTCpyoeszhacM4hLDXJA/b5Xas4CfaSG5ZdPVXyZAF2TfKDWy1nTa npuXqAPUzEfxN41a9E3JaH+cz1yuTwRLogHzntiCmHzD2gcRfTLc6D5MUVwhyZ+NZ1S5A W3Y+ROsvGWnN8eHqOhSM8xAX4ttzSIs/UL8ulsLEbyyfq6RmixMSH5LZDFfH1LahO/w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792635311; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=+QZSiUEYn0W4pnIl93mx13ch2e9Wbsv7HlE1Ei2zCpQ=; b=dDOpmqh5Z30UX05W8iffNyIW0t9vhpRn4ozZizZ8HiB2bbAPn/GLaiDlhRk8y3meY4v6 LBD2szfMp7A8YxI66Yi1OVTDJ/2+kp39BRjHnZCejycJDx+imHBCgeRBUuaIjYBi9Mo14 WNFmrBa1ZiLZk29INV4OwWotsVojr5VL0cIOeW1P1GUwWsmSL8UVFvYEXymK5KYTnY/TL p+dnRCDOgZ3oYfiMdnvt/zNk4z3L7hHg3nC4FBOxmVgR9DQ7NQ0jobkH9AYP4+J78qSj5 LM81rtdSDRzXvQTnTK+qEzIXw/5kkmtLlOZ4zGQZA43Uoqopd9nqUuqo/Rah2KXRI4g== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=NsQAbmr6; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 681F6606A320 for ; Thu, 22 Oct 2026 02:15:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=NsQAbmr6 Received: by smtp.kernel.org (Postfix) with ESMTPSA id C2BC41F000C1; Thu, 22 Oct 2026 02:15:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792635311; bh=+QZSiUEYn0W4pnIl93mx13ch2e9Wbsv7HlE1Ei2zCpQ=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=NsQAbmr6U9+ZMsV+bDg4Re/+urEgxxX/gYMHvv6ZlKDHgoo0NLYkxPCMx/afo3Xfv bZou9/0IJbmmmqbP64/UuxpfRq1Asjx/a136h/QX5JTfx0XdSJFQR0TPMBNyQ+MW+o d4jEcCY/YWq37HsLoLXmf1fxKNck2V3yogocFixpNrlnaxUaI0jXFc7YVMSWm5Ytbg s5pENPot8Lf8N+0GGkG8KiyhLkHpIDGQCc7p5j6xGRqRrHiwpbbG8BxC5HjBg1QXPG KsK4mnx/km6JK5xvEEFye35bR3zbFhTV2HXGj0ib7tvmBydzYelIIvtBzeXn12zOPs ylD25l95tkYBQ== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH bpf-next 6/9] uprobes: Don't sleep on mmap_lock with dup_mmap_sem held in dup_mmap() Reply-To: sashiko-reviews@lists.linux.dev To: "Alexei Starovoitov" Cc: linux-perf-users@vger.kernel.org In-Reply-To: <20261022015712.1297331-7-alexei.starovoitov@gmail.com> References: <20261022015712.1297331-1-alexei.starovoitov@gmail.com> <20261022015712.1297331-7-alexei.starovoitov@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 22 Oct 2026 02:15:10 +0000 X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > From: Alexei Starovoitov >=20 > dup_mm() takes dup_mmap_sem for reading and then dup_mmap() sleeps on > mmap_lock of the parent. When another thread keeps that mmap_lock busy > register_for_each_vma() waits for the reader, and every other fork() in > the system waits for the writer. The parent doesn't have to map the file: >=20 > A thread 1: mmap(MAP_POPULATE) -> mmap_read_lock(A) > A thread 2: fork() -> percpu_down_read(&dup_mmap_sem), > mmap_write_lock_killable(A) sleeps > tracer: percpu_down_write(&dup_mmap_sem) sleeps > others: fork() -> percpu_down_read(&dup_mmap_sem) sleeps >=20 > dup_mmap() needs both locks. Don't sleep on one of them while holding > the other. Sleep on mmap_lock and trylock dup_mmap_sem. If that fails sle= ep > [ ... ] > perf_event, 4 uprobes 419 (424) 0.10 (0.44) 632 11.4 >=20 > During detach: 265-293 -> 0.19-0.37. >=20 > Signed-off-by: Alexei Starovoitov Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261022015712.1297= 331-1-alexei.starovoitov@gmail.com?part=3D6