From nobody Wed Dec 17 17:39:13 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 From nobody Wed Dec 17 17:39:13 2025 Received: from out-189.mta0.migadu.com (out-189.mta0.migadu.com [91.218.175.189]) (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 23CA227A929 for ; Fri, 3 Oct 2025 08:47:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.189 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759481238; cv=none; b=TfU0481Zcuf91KxKqaIYAgFJBQEVAk+ugLQSHHPRMnJqbA9hoZ4jDP57PNOWu51ggUyp+BJjpAAbyOrBHmUyGtUD9jLm95LbvNWNI6/+TdHAmaVpW7AtNvy8lmHfebWuAB5j2LcZMHyKLKeonLY1czESkeJpMgNEZMT/+OyGUgw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759481238; c=relaxed/simple; bh=XLodWl1Mnqi6n+xmZaM4r4KxwmmAoji2W6kZJLMVLA8=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Qy96/zeVsQWPcv544LAR07azUGtfTPH+p6k260257N/mDuXEoF6+1bxEd1mIyz22Z7qaNIqfShGhSYDSVBHdLtsg1mR4hybZeMCiVf+f/P7nvaKomG3ajJ7cOTBjdthhMu9TYSxehQwuhRbZJTXPanRqWpkKTmjHGTdTaamkkeI= 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=uUksfYjQ; arc=none smtp.client-ip=91.218.175.189 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="uUksfYjQ" 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=1759481235; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=CZM6bExjDs8jz6TVsKvY1N151Suvl2rvzQSjV8ALYIE=; b=uUksfYjQzFzSy+jIUVRgc1r4bn38I5hd+45qOv9/mdFxrvxzk9fcv6zH0laC2n+GqUwYYK LkUwLZKnFojni7xbzvB9JkN87RKhExIzunDQfsiFzpCqzTXr8rFazFgRGqVbh9NlKL6jqy GuCU2BX8K3WYSi4giFgDNlfM4rFjHUA= 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 Subject: [PATCH bpf 2/2] selftests/bpf: Add test for unpinning htab with internal timer struct Date: Fri, 3 Oct 2025 16:45:28 +0800 Message-ID: <20251003084528.502518-3-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" Add test to verify that unpinning hash tables containing internal timer structures does not trigger context warnings. Each subtest (timer_prealloc and timer_no_prealloc) can trigger the context warning when unpinning, but the warning cannot be triggered twice within a short time interval (a HZ), which is expected behavior. Signed-off-by: KaFai Wan --- .../selftests/bpf/prog_tests/pinning_htab.c | 37 +++++++++++++++++++ .../selftests/bpf/progs/test_pinning_htab.c | 25 +++++++++++++ 2 files changed, 62 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/pinning_htab.c create mode 100644 tools/testing/selftests/bpf/progs/test_pinning_htab.c diff --git a/tools/testing/selftests/bpf/prog_tests/pinning_htab.c b/tools/= testing/selftests/bpf/prog_tests/pinning_htab.c new file mode 100644 index 000000000000..fc804bb87b26 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/pinning_htab.c @@ -0,0 +1,37 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include "test_pinning_htab.skel.h" + +static void unpin_map(const char *map_name, const char *pin_path) +{ + struct test_pinning_htab *skel; + struct bpf_map *map; + int err; + + skel =3D test_pinning_htab__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel open_and_load")) + return; + + map =3D bpf_object__find_map_by_name(skel->obj, map_name); + if (!ASSERT_OK_PTR(map, "bpf_object__find_map_by_name")) + goto out; + + err =3D bpf_map__pin(map, pin_path); + if (!ASSERT_OK(err, "bpf_map__pin")) + goto out; + + err =3D bpf_map__unpin(map, pin_path); + if (!ASSERT_OK(err, "bpf_map__unpin")) + goto out; +out: + test_pinning_htab__destroy(skel); +} + +void test_pinning_htab(void) +{ + if (test__start_subtest("timer_prealloc")) + unpin_map("timer_prealloc", "/sys/fs/bpf/timer_prealloc"); + if (test__start_subtest("timer_no_prealloc")) + unpin_map("timer_no_prealloc", "/sys/fs/bpf/timer_no_prealloc"); +} diff --git a/tools/testing/selftests/bpf/progs/test_pinning_htab.c b/tools/= testing/selftests/bpf/progs/test_pinning_htab.c new file mode 100644 index 000000000000..ae227930c73c --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_pinning_htab.c @@ -0,0 +1,25 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "vmlinux.h" +#include + +char _license[] SEC("license") =3D "GPL"; + +struct timer_val { + struct bpf_timer timer; +}; + +struct { + __uint(type, BPF_MAP_TYPE_HASH); + __type(key, __u32); + __type(value, struct timer_val); + __uint(max_entries, 1); +} timer_prealloc SEC(".maps"); + +struct { + __uint(type, BPF_MAP_TYPE_HASH); + __type(key, __u32); + __type(value, struct timer_val); + __uint(max_entries, 1); + __uint(map_flags, BPF_F_NO_PREALLOC); +} timer_no_prealloc SEC(".maps"); --=20 2.43.0