From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 EAEF31BDA95; Mon, 10 Feb 2025 08:43:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739177023; cv=none; b=NcVPc3GG6UgkCafLZhWVH38rh/x8Em2CnQE0fIUgs2r1rsPChW53trhakp/Sh+Pg7cyqnv0uzP6e3ndKGK8Jo7OStl4QN+EwMm3j0LSnmnmEUFNhIAk+J+I3YGnXM2HnyTu5rahklMKvsO6JQxgUxFrYam8yuLGNHBimBFK7Ca0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739177023; c=relaxed/simple; bh=Mdg0SrPX+N0sJvGRpoqt/A0aLHrXFS32YIG1eZopRI0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=MjXDQBfYJFAIMa4Qc/wyvWkomtwJyru93Gx4Eq0b1oh6/v6occebSvBITT8mVxDUECRl1l3V40/j0dKKp/99i5uDnBZ/visuPkXQ0xXSQMPiXSQYZUxe0ohNiTC9OqUL60IB2UCCdGIWgwaXTABNbbOLVNjw9WSnCr96s9PnAPw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=R4Nz+1Og; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=s0ARSOsA; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="R4Nz+1Og"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="s0ARSOsA" Date: Mon, 10 Feb 2025 09:43:31 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1739177013; h=from:from: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; bh=cIuRcjptjh9/AMgIrM80ZU522dtLicptkr1+Q41B1sE=; b=R4Nz+1OgIWm/jaJ40jwvDEJHT0xx6tsCC8J2gX+2mQTo+oBAmRxO6UokMjwj/IYy33qYOA UALDMy1n83bp2tBYJ63ObnptX0CCTzXxql0psHe4MwnMmmAN0ETpzGvSsNEJkzfbANBIvX jdn7czu/GuLkDZArqYBV3A3wzYxxKc8Em4jFLF1lZPqoWf6cRkxGcmT2KqBAsnHRTbllNa bkdaRpPb8luWXjWIaFnRpsG691WEu8IPzyrSvl6bhFdczyDtaubgf+iQp1VOTpHZo2aaVQ DRpcHsrnKohSa//0a08k+OoBhEh6B/rgj95X4E9NgfeWzn5s7PMrQuHA84OWXA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1739177013; h=from:from: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; bh=cIuRcjptjh9/AMgIrM80ZU522dtLicptkr1+Q41B1sE=; b=s0ARSOsALs0PNUGuLU7s1AfucQpyJovs44nzK0JRkeXQ3tDazfk0Q491HyzlAuTiLiojBC OZF1Dn4qxpHH+eDw== From: Sebastian Andrzej Siewior To: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Michal =?utf-8?Q?Koutn=C3=BD?= , "Paul E. McKenney" , Boqun Feng , Greg Kroah-Hartman , Hillf Danton , Johannes Weiner , Marco Elver , Tejun Heo , tglx@linutronix.de, Andrii Nakryiko , Eduard Zingerman , Mykola Lysenko , bpf@vger.kernel.org Subject: Re: [PATCH v7 5/6] kernfs: Use RCU to access kernfs_node::parent. Message-ID: <20250210084331.IJB3qKdl@linutronix.de> References: <20250203135023.416828-1-bigeasy@linutronix.de> <20250203135023.416828-6-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20250203135023.416828-6-bigeasy@linutronix.de> On 2025-02-03 14:50:22 [+0100], To cgroups@vger.kernel.org wrote: > kernfs_rename_lock is used to obtain stable kernfs_node::{name|parent} > pointer. This is a preparation to access kernfs_node::parent under RCU > and ensure that the pointer remains stable under the RCU lifetime > guarantees. =E2=80=A6 The robot complained that the selftests for bpf broke. As it turns out, the tests access kernfs_node::{parent|name} and after the rename ::parent is gone so it does not compile. If there are no objections, I would merge this into 5/6 and repost. "test_progs -a test_profiler" passes. diff --git a/tools/testing/selftests/bpf/progs/profiler.inc.h b/tools/testi= ng/selftests/bpf/progs/profiler.inc.h index 8bd1ebd7d6afd..a4f518ee5f4de 100644 --- a/tools/testing/selftests/bpf/progs/profiler.inc.h +++ b/tools/testing/selftests/bpf/progs/profiler.inc.h @@ -223,7 +223,7 @@ static INLINE void* read_full_cgroup_path(struct kernfs= _node* cgroup_node, if (bpf_cmp_likely(filepart_length, <=3D, MAX_PATH)) { payload +=3D filepart_length; } - cgroup_node =3D BPF_CORE_READ(cgroup_node, parent); + cgroup_node =3D BPF_CORE_READ(cgroup_node, __parent); } return payload; } @@ -300,6 +300,7 @@ static INLINE void* populate_cgroup_info(struct cgroup_= data_t* cgroup_data, cgroup_data->cgroup_proc_length =3D 0; cgroup_data->cgroup_full_length =3D 0; =20 + bpf_rcu_read_lock(); size_t cgroup_root_length =3D bpf_probe_read_kernel_str(payload, MAX_PATH, BPF_CORE_READ(root_kernfs, name)); @@ -323,6 +324,7 @@ static INLINE void* populate_cgroup_info(struct cgroup_= data_t* cgroup_data, cgroup_data->cgroup_full_length =3D payload_end_pos - payload; payload =3D payload_end_pos; } + bpf_rcu_read_unlock(); =20 return (void*)payload; } --=20 2.47.2 Sebastian