From nobody Mon Sep 28 08:07:53 2026 Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) (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 CA5FE453A50; Mon, 24 Aug 2026 16:56:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=82.195.75.108 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787590613; cv=none; b=cLUBbHfoDPP9yLtU5qebEITqOtCFNc1jkpm8P8ZjURK4wMmviCAsteDiSqTgScNR5Dopi2p+TampZtfxNIcNcsZHdRAQot8JFjgeIE4I+PZduT37kXVV5sZWLme7MryOgb9tiRAE0V0F8ueZMlyV+HX74RDzecglrvewjUGMJuw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787590613; c=relaxed/simple; bh=V2A9Axf7eE9xL6yG3yuTTEdXmEZ+WMWwbGsBsB7Lq3Q=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=ZWwj39FeQi6ZLi2oVvxKHybYfTkVkVjaq2FIE7sq2DOtCquL80LiL7TbrSHy4GwCB6wy8F5Xo6cjgm4BXwDmdfsCDsHQZUesUjfNc9l0mz3s1Byc4vIRGkaaIqkKctuq227dGzAzwerwCgavpJ/BWnBsysf9IU/2VDLjzC1Zdy8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org; spf=pass smtp.mailfrom=debian.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b=Vvo8cpbR; arc=none smtp.client-ip=82.195.75.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=debian.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b="Vvo8cpbR" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:Cc:To:Message-Id: Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date:From: Reply-To:Content-ID:Content-Description:In-Reply-To:References; bh=ZJEJt/1OFWocyoYWJNDaWaIZqTVtqPtpuU0Zo1lyjtU=; b=Vvo8cpbRbyAYE8L00wPMZX1yqJ 9XdWTZd37kxqYV7o7+O6XVBwARSseFhLdYSaaZ/UpkWPj/xK+v12Zv+auZ09gAhSd9nPqHeGTPf3i +iRn75M5sYUZ72wKrxICOIRinH4MU9teEtLnZYqmrBKCA4FUxRO6ZDKZ8Ak/PDVEq9X+njGjdYFiR Twy7X2M+Mv5gEbULDxqPZ6bE9fRCZXHoAF+TWl4FoP/FL1+lw4htbNvGBK3fxD3YVXRWzDGoOdqee X9n02NAMkc+StJYX4ZvIXnVkBSyrzDxqfr136PQ1yfFEZMB0r7kK4eDHvMFR/frcNxN4W2CNiZWDa QAB05kRQ==; Received: from authenticated-user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1wyXyX-00DoHP-1B; Mon, 24 Aug 2026 16:56:45 +0000 From: Breno Leitao Date: Mon, 24 Aug 2026 09:54:10 -0700 Subject: [PATCH] bpf: arena: reschedule while freeing the arena pages Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260824-b4-bpf-arena-free-resched-v1-1-5c447477a64b@debian.org> X-B4-Tracking: v=1; b=H4sIADF3jGoC/x2MwQqAIBAFfyX23IJJRPUr0UHtWXuxWCEC6d+TY C5zmCmUoYJMc1NIcUuWM1Xp2obC4dIOlq06WWMHM9qefeWK7BTJcVSAFTkc2BjWeGfgx6mbqPa XIsrzv5f1fT9uZI5UawAAAA== X-Change-ID: 20260824-b4-bpf-arena-free-resched-e20ba0eb8919 To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Barret Rhoden Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Breno Leitao X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=1642; i=leitao@debian.org; h=from:subject:message-id; bh=V2A9Axf7eE9xL6yG3yuTTEdXmEZ+WMWwbGsBsB7Lq3Q=; b=owEBbQKS/ZANAwAIATWjk5/8eHdtAcsmYgBqjHfJ5K/n/Y/pBhTVoT1tzqS8PjxMSdeqOKi1A U2cB/3SAcKJAjMEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCaox3yQAKCRA1o5Of/Hh3 baKNEACM6DG2tpGJCIDtriGaj0W47AQn+xNwc3HcIsPv/hCCUi5NqYnM3/3AiyNbz4qMSoAn2nx 3IvebhCYlolZ/P6YUmI93AbSeppPleha+bcSUW7uqdeXX4olssF6b2jO2aDpbem9y3Tn/FCdu8M RHQVZgLlr/6aswv6bcLLYIxNf8F+9hMib7K58oP/+z8qMRunWcDcz7vLR2UQLbbzbLwnp3kCef3 EEP2/R3vRs9Fsicd311VSh9TkHw5EDkE2w58aVS1MCpwpwMiaI5xl2Vrx0J8B0KtzDPpuc5xlIQ MDhGbo6aL7NaBWnC+HXrO5Ql7EWW6rbJi+2bmxuN1G6FBRvLQjVyBQV+AaGczHtbqMARsyTEq1D LaLkP8sOJFQGJrH5DgdBK1Kr5pTnJRSLspk/P2q7+xZ3uO3zOS11VpvC+rlskXngfA1QKxK5HCf uz1PGRSAKBorOqVL373wRQ8m/eB3eHiMiozVUy2K+cqxQO43TlDXsgZpjHfaM3D02ymtHGLROiT 1KjwwiPYdQoPKdHnEuRdpOqMUUt/2Ie2qQkl8sp30imats+Ai+yY6pU0GTkMBvJNml0P1OUCrsn 2zbvYj4zRuomto7FJEEXMsIZyIs9iuipGa5BfehkPEnITBzNfktrnLcFGwcC8gYOvq60iUWA6dU kd4nh9Tbf/TxmAg== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D X-Debian-User: leitao On non-preemptible kernels that is long enough to trip both the RCU stall detector and the softlockup watchdog. Observed on production arm64 hosts at Meta: rcu: INFO: rcu_sched self-detected stall on CPU rcu: 37-....: (20999 ticks this GP) idle=3D3834/1/0x4000000000000000 Workqueue: events_unbound bpf_map_free_deferred Call trace: __apply_to_page_range+0x404/0x518 apply_to_existing_page_range+0x18/0x28 arena_map_free+0x54/0x98 bpf_map_free_deferred+0x70/0xf8 process_scheduled_works+0x17c/0x400 worker_thread+0x198/0x498 [...] watchdog: BUG: soft lockup - CPU#37 stuck for 44s! [kworker/u288:15] Kernel panic - not syncing: softlockup: hung tasks arena_map_free() sweeps the whole 4GiB arena address range in a single apply_to_existing_page_range() call and drops every populated page from the walk callback. Give up the CPU after releasing each page, using cond_resched(). Fixes: 317460317a02 ("bpf: Introduce bpf_arena.") Signed-off-by: Breno Leitao --- kernel/bpf/arena.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c index 7b6847200b431..c5f6bebbb15c3 100644 --- a/kernel/bpf/arena.c +++ b/kernel/bpf/arena.c @@ -364,6 +364,7 @@ static int existing_page_cb(pte_t *ptep, unsigned long = addr, void *data) * the freed page. So it all relies on 1. */ __free_page(page); + cond_resched(); return 0; } =20 --- base-commit: 0a0d1d55dad570724bf8c7ea83409639cfb4be9b change-id: 20260824-b4-bpf-arena-free-resched-e20ba0eb8919 Best regards, -- =20 Breno Leitao