From nobody Wed Dec 17 19:17:01 2025 Received: from out-181.mta0.migadu.com (out-181.mta0.migadu.com [91.218.175.181]) (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 E2A1D275AF2; Fri, 3 Oct 2025 08:47:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.181 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759481233; cv=none; b=oB2zVi/O4p8dVFNLjAiaFDkg3zDrT7QuXXSvzyiuZP9q4vPldFST38l663XkXfpY4OEhiqQkxPzgBXXd2w3hopOQZmTZSpD2hEQA43XZS+e8dGN3L25YwASeuRel97q/WTnFgU+j+3z1Le5Yzkyl1Y2vRlhLLPUVEz0p2Dd8fCY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759481233; c=relaxed/simple; bh=KdhvngRIzUvJjCKOe7aQRI/7vJZpSB4qLpuJxx/8jSo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CNeYmTLLQs79/quEudc+uLv8rBP7DE2KfFZK0oAs966XtIrmt24hszwvlnrArYD9WbBRDxu/sbqjq4PB8iiPbIaDRBsOnQm8TYuYCY4vze7uutPkAv1d1wT2DO5JPX/HSYbMsiO7wbgzVqAkrOpvsoTnY4PLIUu5nH3i0emgtLU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=LiPXq2mb; arc=none smtp.client-ip=91.218.175.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="LiPXq2mb" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1759481228; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=N+ayMPxTFn1sqgrWQClbx3xLTMHfXKLiK2Xn5bMQL3I=; b=LiPXq2mbY9BWD0v/aKVD5QN0EUAPZQrjkH4EvcwQqECr1mC99hYQNOG6OFf/P4Uk+NxNhI cb6RjlZHblng/T1iLji1uHP0KUzlN3KZhguvTxDh1uaJND70TOiWSdzLqkzkXYsjlv5dVL nCEzg4VrLSniCmt+KwAf8QlXHIrv3Pg= From: KaFai Wan To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, kafai.wan@linux.dev, toke@redhat.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: Le Chen Subject: [PATCH bpf 1/2] bpf: Avoid RCU context warning when unpinning htab with internal structs Date: Fri, 3 Oct 2025 16:45:27 +0800 Message-ID: <20251003084528.502518-2-kafai.wan@linux.dev> In-Reply-To: <20251003084528.502518-1-kafai.wan@linux.dev> References: <20251003084528.502518-1-kafai.wan@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" When unpinning a BPF hash table (htab or htab_lru) that contains internal structures (timer, workqueue, or task_work) in its values, a BUG warning is triggered: BUG: sleeping function called from invalid context at kernel/bpf/hashtab.c= :244 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 14, name: ksoftirqd= /0 ... The issue arises from the interaction between BPF object unpinning and RCU callback mechanisms: 1. BPF object unpinning uses ->free_inode() which schedules cleanup via call_rcu(), deferring the actual freeing to an RCU callback that executes within the RCU_SOFTIRQ context. 2. During cleanup of hash tables containing internal structures, htab_map_free_internal_structs() is invoked, which includes cond_resched() or cond_resched_rcu() calls to yield the CPU during potentially long operations. However, cond_resched() or cond_resched_rcu() cannot be safely called from atomic RCU softirq context, leading to the BUG warning when attempting to reschedule. Fix this by changing from ->free_inode() to ->destroy_inode() for BPF objects (prog, map, link). This allows direct inode freeing without RCU callback scheduling, avoiding the invalid context warning. Reported-by: Le Chen Closes: https://lore.kernel.org/all/1444123482.1827743.1750996347470.JavaMa= il.zimbra@sjtu.edu.cn/ Fixes: 68134668c17f ("bpf: Add map side support for bpf timers.") Suggested-by: Alexei Starovoitov Signed-off-by: KaFai Wan --- kernel/bpf/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index f90bdcc0a047..65c2a71d7de1 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -790,7 +790,7 @@ const struct super_operations bpf_super_ops =3D { .statfs =3D simple_statfs, .drop_inode =3D inode_just_drop, .show_options =3D bpf_show_options, - .free_inode =3D bpf_free_inode, + .destroy_inode =3D bpf_free_inode, }; =20 enum { --=20 2.43.0