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Mon, 29 Jul 2024 22:34:48 -0400 X-MC-Unique: 659DcF95N4KkpuWSPfN_Kg-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 68C3018B64A5; Tue, 30 Jul 2024 02:34:40 +0000 (UTC) Received: from [10.2.16.36] (unknown [10.2.16.36]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 5B4501955D59; Tue, 30 Jul 2024 02:34:38 +0000 (UTC) Message-ID: <0ba00b7c-5292-4242-b648-4ca8d4a457c6@redhat.com> Date: Mon, 29 Jul 2024 22:34:37 -0400 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] cgroup/cpuset: fix panic caused by partcmd_update To: Chen Ridong , tj@kernel.org, lizefan.x@bytedance.com, hannes@cmpxchg.org, adityakali@google.com, sergeh@kernel.org Cc: bpf@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240730015316.2324188-1-chenridong@huawei.com> Content-Language: en-US From: Waiman Long In-Reply-To: <20240730015316.2324188-1-chenridong@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On 7/29/24 21:53, Chen Ridong wrote: > We find a bug as below: > BUG: unable to handle page fault for address: 00000003 > PGD 0 P4D 0 > Oops: 0000 [#1] PREEMPT SMP NOPTI > CPU: 3 PID: 358 Comm: bash Tainted: G W I 6.6.0-10893-g60d6 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/4 > RIP: 0010:partition_sched_domains_locked+0x483/0x600 > Code: 01 48 85 d2 74 0d 48 83 05 29 3f f8 03 01 f3 48 0f bc c2 89 c0 48 9 > RSP: 0018:ffffc90000fdbc58 EFLAGS: 00000202 > RAX: 0000000100000003 RBX: ffff888100b3dfa0 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000002fe80 > RBP: ffff888100b3dfb0 R08: 0000000000000001 R09: 0000000000000000 > R10: ffffc90000fdbcb0 R11: 0000000000000004 R12: 0000000000000002 > R13: ffff888100a92b48 R14: 0000000000000000 R15: 0000000000000000 > FS: 00007f44a5425740(0000) GS:ffff888237d80000(0000) knlGS:0000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000100030973 CR3: 000000010722c000 CR4: 00000000000006e0 > Call Trace: > > ? show_regs+0x8c/0xa0 > ? __die_body+0x23/0xa0 > ? __die+0x3a/0x50 > ? page_fault_oops+0x1d2/0x5c0 > ? partition_sched_domains_locked+0x483/0x600 > ? search_module_extables+0x2a/0xb0 > ? search_exception_tables+0x67/0x90 > ? kernelmode_fixup_or_oops+0x144/0x1b0 > ? __bad_area_nosemaphore+0x211/0x360 > ? up_read+0x3b/0x50 > ? bad_area_nosemaphore+0x1a/0x30 > ? exc_page_fault+0x890/0xd90 > ? __lock_acquire.constprop.0+0x24f/0x8d0 > ? __lock_acquire.constprop.0+0x24f/0x8d0 > ? asm_exc_page_fault+0x26/0x30 > ? partition_sched_domains_locked+0x483/0x600 > ? partition_sched_domains_locked+0xf0/0x600 > rebuild_sched_domains_locked+0x806/0xdc0 > update_partition_sd_lb+0x118/0x130 > cpuset_write_resmask+0xffc/0x1420 > cgroup_file_write+0xb2/0x290 > kernfs_fop_write_iter+0x194/0x290 > new_sync_write+0xeb/0x160 > vfs_write+0x16f/0x1d0 > ksys_write+0x81/0x180 > __x64_sys_write+0x21/0x30 > x64_sys_call+0x2f25/0x4630 > do_syscall_64+0x44/0xb0 > entry_SYSCALL_64_after_hwframe+0x78/0xe2 > RIP: 0033:0x7f44a553c887 > > It can be reproduced with cammands: > cd /sys/fs/cgroup/ > mkdir test > cd test/ > echo +cpuset > ../cgroup.subtree_control > echo root > cpuset.cpus.partition > echo 0-3 > cpuset.cpus // 3 is nproc What do you mean by "3 is nproc"? Are there only 3 CPUs in the system? What are the value of /sys/fs/cgroup/cpuset.cpu*? > > This issue is caused by the incorrect rebuilding of scheduling domains. > In this scenario, test/cpuset.cpus.partition should be an invalid root > and should not trigger the rebuilding of scheduling domains. When calling > update_parent_effective_cpumask with partcmd_update, if newmask is not > null, it should recheck newmask whether there are cpus is available > for parect/cs that has tasks. > > Fixes: 0c7f293efc87 ("cgroup/cpuset: Add cpuset.cpus.exclusive.effective for v2") > Signed-off-by: Chen Ridong > --- > kernel/cgroup/cpuset.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > index 40ec4abaf440..a9b6d56eeffa 100644 > --- a/kernel/cgroup/cpuset.c > +++ b/kernel/cgroup/cpuset.c > @@ -1991,6 +1991,8 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, > part_error = PERR_CPUSEMPTY; > goto write_error; > } > + /* Check newmask again, whether cpus are available for parent/cs */ > + nocpu |= tasks_nocpu_error(parent, cs, newmask); > > /* > * partcmd_update with newmask: The code change looks reasonable to me. However, I would like to know more about the reproduction steps. Cheers, Longman