From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E0D5E1A01D8 for ; Mon, 23 Sep 2024 18:21:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727115671; cv=none; b=nMGUCo4eaTz2liqs5SNVeRH8SOe4aZvvu+QGXzXwAsL26bqpG/R9Iv7Y7ZbKfigJJWhU3kgZCpW3m9gckejhf+W87aBByFTvNh7wNGkTAniJAWT9De/gNYjkZpzL3hpZ/giS9FTPj10FCm2z4sK3UA2VjZmCLsgixlyjO1h4nTU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727115671; c=relaxed/simple; bh=4W+9+uEw6U1YUmQUoFTtj9ci4w6gAz42P/CEX2pKqX0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hdn0zRe5LnK5oBTxtlfofu27t+/97AlFOdhueLKXRA3p+/UVUPOYum7Me2AGOPwosZhV8umMD/t2eYd/3plpOIqkpfkp+q+1p1a9qyOZ7qN+Vhw2JWqBgVTDVUf63bKP4xdi6dpG55dgryPq4IWx3YaFSKkCSs1F7+lc1thlWaw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oJAqAQYX; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oJAqAQYX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40177C4CECD; Mon, 23 Sep 2024 18:21:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727115670; bh=4W+9+uEw6U1YUmQUoFTtj9ci4w6gAz42P/CEX2pKqX0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oJAqAQYX2Me9NV5XuqSplePKRPzaLC0axJUlq7n0O7OANu2zP999vFf6yLqsBWH/P GeGzXgXm8yCl13Rmz53xP4wnc4iSxjxn7czAR8Oyf3FS4QMCGlqbI4T0gVYistH5Hi jV0dL/fiFU53yL7t9HJzP+pkA9F1ZRBRADb2nHA4/wLFTIF4FiQmSs8V+6CHke22OI cCN6W4ry0hDVVSPd7zKTQMIbYpNN5NighfsI0v/qv/5hTQFqVDUWCCfnZsCz31kyuC 0RcRjnLPVVVb8vlZam7fF0UwcUOdBOgwjKEFwsR3qX2E1nD2Q4h+HSGdMRDRPgTwVS iCC2d5aQ/HRkQ== Date: Mon, 23 Sep 2024 08:21:09 -1000 From: Tejun Heo To: Aboorva Devarajan Cc: void@manifault.com, linux-kernel@vger.kernel.org, Alexei Starovoitov , Andrii Nakryiko Subject: Re: [sched_ext/for-6.11]: Issue with BPF Scheduler during CPU Hotplug Message-ID: References: <3da12c96daecaa055c478816f5e86c7b44a04d53.camel@linux.ibm.com> <516106abdf5c922ee19dffd9eb69ea3f9e20e54a.camel@linux.ibm.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <516106abdf5c922ee19dffd9eb69ea3f9e20e54a.camel@linux.ibm.com> Hello, (cc'ing Alexei and Andrii for the BPF part) On Mon, Sep 23, 2024 at 08:26:32PM +0530, Aboorva Devarajan wrote: > Sharing the crash logs observed in PowerPC here for general reference, FYI: > > [ 8638.891964] Kernel attempted to read user page (a8) - exploit attempt? (uid: 0) > [ 8638.892002] BUG: Kernel NULL pointer dereference on read at 0x000000a8 > [ 8638.892019] Faulting instruction address: 0xc0000000004e7cc0 > [ 8638.892038] Oops: Kernel access of bad area, sig: 11 [#1] > [ 8638.892060] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA PowerNV > [ 8638.892080] Modules linked in: nf_conntrack_netlink nfnetlink xfrm_user xfrm_algo xt_addrtype > br_netfilter xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp > ip6table_mangle ip6table_nat iptable_mangle iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 > nf_defrag_ipv4 ebtable_filter ebtables vhost_vsock vmw_vsock_virtio_transport_common ip6tabl > e_filter ip6_tables vhost vhost_iotlb iptable_filter vsock bridge stp llc kvm_hv kvm joydev > input_leds mac_hid at24 ofpart cmdlinepart uio_pdrv_genirq ibmpowernv opal_prd ipmi_powernv > powernv_flash uio binfmt_misc sch_fq_codel nfsd mtd ipmi_devintf ipmi_msghandler auth_rpcgss > jc42 ramoops reed_solomon ip_tables x_tables autofs4 raid10 raid456 async_raid6_recov async > _memcpy async_pq async_xor async_tx raid1 raid0 dm_mirror dm_region_hash dm_log mlx5_ib ib_uverbs > ib_core mlx5_core hid_generic usbhid hid ast i2c_algo_bit drm_shmem_helper drm_kms_hel > per vmx_crypto drm mlxfw crct10dif_vpmsum crc32c_vpmsum psample tls tg3 ahci libahci > drm_panel_orientation_quirks > [ 8638.892621] CPU: 62 UID: 0 PID: 5591 Comm: kworker/62:2 Not tainted 6.11.0-rc4+ #2 > [ 8638.892663] Hardware name: 8335-GTW POWER9 0x4e1203 opal:skiboot-v6.5.3-35-g1851b2a06 PowerNV > [ 8638.892693] Workqueue: events bpf_prog_free_deferred > [ 8638.892735] NIP: c0000000004e7cc0 LR: c0000000004e7bbc CTR: c0000000003a9b30 > [ 8638.892798] REGS: c000000ea4cbf7f0 TRAP: 0300 Not tainted (6.11.0-rc4+) > [ 8638.892862] MSR: 9000000000009033 CR: 42a00284 XER: 00000000 > [ 8638.892915] CFAR: c0000000004e7bb8 DAR: 00000000000000a8 DSISR: 40000000 IRQMASK: 1 > [ 8638.892915] GPR00: c0000000004e7bbc c000000ea4cbfa90 c000000002837f00 0000000000000005 > [ 8638.892915] GPR04: 0000000000000015 0000000000000009 0000000000000009 c000000004840b00 > [ 8638.892915] GPR08: ffffffffffffffff 00000000ffffe000 ffffffffffffffff 000001937b55db50 > [ 8638.892915] GPR12: 0000000000200000 c000007ffdfac300 c0000000031b1fc8 0000000000010000 > [ 8638.892915] GPR16: c00000000000018e 000000007fffffff 0000000000000000 000000000000e1c0 > [ 8638.892915] GPR20: 61c8864680b583eb 0000000000000000 0000000000000000 00000000000de1d5 > [ 8638.892915] GPR24: 0000000000000000 c000000003da4408 c000000003da4400 c000000003da43f8 > [ 8638.892915] GPR24: 0000000000000000 c000000003da4408 c000000003da4400 c000000003da43f8 > [ 8638.892915] GPR28: 0000000000000000 0000000000000000 0000000000000000 c000000ea4cbfa90 > [ 8638.893350] NIP [c0000000004e7cc0] walk_to_pmd+0x80/0x240 > [ 8638.893380] LR [c0000000004e7bbc] __get_locked_pte+0x4c/0xd0 > [ 8638.893398] Call Trace: > [ 8638.893407] [c000000ea4cbfa90] [c000000ea4cbfb20] 0xc000000ea4cbfb20 (unreliable) > [ 8638.893429] [c000000ea4cbfaf0] [c0000000004e7bbc] __get_locked_pte+0x4c/0xd0 > [ 8638.893457] [c000000ea4cbfb40] [c0000000000b1dd0] patch_instructions+0x130/0x630 > [ 8638.893500] [c000000ea4cbfc10] [c000000000123180] bpf_arch_text_invalidate+0x80/0xd0 > [ 8638.893552] [c000000ea4cbfc60] [c0000000003a7508] bpf_prog_pack_free+0x138/0x2f0 > [ 8638.893584] [c000000ea4cbfd10] [c0000000003a7e38] bpf_jit_binary_pack_free+0x48/0xa0 > [ 8638.893617] [c000000ea4cbfd50] [c000000000123258] bpf_jit_free+0x88/0x100 > [ 8638.893667] [c000000ea4cbfd90] [c0000000003a9d70] bpf_prog_free_deferred+0x240/0x280 > [ 8638.893725] [c000000ea4cbfde0] [c0000000001a6828] process_scheduled_works+0x268/0x520 > [ 8638.893767] [c000000ea4cbfee0] [c0000000001a9ed0] worker_thread+0x3f0/0x590 > [ 8638.893809] [c000000ea4cbff80] [c0000000001b37b0] kthread+0x1a0/0x1c0 > [ 8638.893862] [c000000ea4cbffe0] [c00000000000d030] start_kernel_thread+0x14/0x18 > [ 8638.893913] Code: 3cc20157 3b63c4f8 3b45c500 3929c510 3b26c508 3940ffff e87b0000 e8ba0000 > 81290000 e8d90000 38830010 7d494830 7ce42a14 7d2948f8 7d073214 > [ 8638.894003] ---[ end trace 0000000000000000 ]--- > [ 8639.098185] pstore: backend (nvram) writing error (-1) > [ 8639.098205] > [ 8639.098215] note: kworker/62:2[5591] exited with irqs disabled > [ 8798.806603] ------------[ cut here ]------------ > [ 8798.806631] WARNING: CPU: 62 PID: 3769 at kernel/kthread.c:76 kthread_set_per_cpu+0x40/0xd0 > [ 8798.806653] Modules linked in: nf_conntrack_netlink nfnetlink xfrm_user xfrm_algo xt_addrtype > br_netfilter xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp ip6table_mangle > ip6table_nat iptable_mangle iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv > ------------------------------------------------------------------------------------------ > > We will look at this issue as it is specific to PowerPC. This does look like a bug in BPF proper. > But I can confirm that the originally reported hang (deadlock) is no longer present. Great to hear. I'll post the patchset w/ your Tested-by. Thanks. -- tejun