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([240f:74:7be:1:3630:b0a:8446:1dba]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72aad8157e2sm4011665b3a.26.2024.12.20.19.33.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Dec 2024 19:33:35 -0800 (PST) From: Koichiro Den To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] vmstat: disable vmstat_work on vmstat_cpu_down_prep() Date: Sat, 21 Dec 2024 12:33:20 +0900 Message-ID: <20241221033321.4154409-1-koichiro.den@canonical.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 90CF140005 X-Stat-Signature: 4iw7y189ub597mwk6zdhdeztff86r319 X-HE-Tag: 1734752004-499317 X-HE-Meta: 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 GaXsA5C/ 71ZIw/pLCX6sf7zQwFrInkcnLzhruKdcp3uhgayPiRDYXmN+eWngdZDDa09ULNPT86Nb/FwQk69JZrGZtnv4H/SRIwICkGqm4eRWEEfHn9BUcAVsktA7wwhE6Je9GL2hbt85iFXR5DIr2TZHUdEsrZOtAofJsWV7OcwClHRPtF9kcSfqrL1urHKxMwc/sqlarMyRK4yS2i956TgZrLufbCUQ1T9LwNxC/ECglJ13w5wEVLtLRfFaoajKuprAwZaKsUkIGYae5DWxGc09rkmNgT4K8eDETW/xkVCdtKixX2/Xg6r2WKOFMypeknkj49vG7KO1WafBq/NerB+9fXP0i4uF8Xvpmwbf0G8I3wJo3DaRg1IRjX0F4LCcJc4DYt4U/b7cJ3sxe4zm1QQHu30PnE4aazWk1fj7boE19F+RbVoCWwu9Z7Zm8qri65biJQ3g1VFazHyspFHM30SYIYbbwUqsKjw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.275234, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Even after mm/vmstat:online teardown, shepherd may still queue work for the dying cpu until the cpu is removed from online mask. While it's quite rare, this means that after unbind_workers() unbinds a per-cpu kworker, it potentially runs vmstat_update for the dying CPU on an irrelevant cpu before entering atomic AP states. When CONFIG_DEBUG_PREEMPT=y, it results in the following error with the backtrace. BUG: using smp_processor_id() in preemptible [00000000] code: \ kworker/7:3/1702 caller is refresh_cpu_vm_stats+0x235/0x5f0 CPU: 0 UID: 0 PID: 1702 Comm: kworker/7:3 Tainted: G Tainted: [N]=TEST Workqueue: mm_percpu_wq vmstat_update Call Trace: dump_stack_lvl+0x8d/0xb0 check_preemption_disabled+0xce/0xe0 refresh_cpu_vm_stats+0x235/0x5f0 vmstat_update+0x17/0xa0 process_one_work+0x869/0x1aa0 worker_thread+0x5e5/0x1100 kthread+0x29e/0x380 ret_from_fork+0x2d/0x70 ret_from_fork_asm+0x1a/0x30 So, for mm/vmstat:online, disable vmstat_work reliably on teardown and symmetrically enable it on startup. Signed-off-by: Koichiro Den --- v1: https://lore.kernel.org/all/20241220134234.3809621-1-koichiro.den@canonical.com/ --- mm/vmstat.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/vmstat.c b/mm/vmstat.c index 4d016314a56c..0889b75cef14 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -2148,13 +2148,14 @@ static int vmstat_cpu_online(unsigned int cpu) if (!node_state(cpu_to_node(cpu), N_CPU)) { node_set_state(cpu_to_node(cpu), N_CPU); } + enable_delayed_work(&per_cpu(vmstat_work, cpu)); return 0; } static int vmstat_cpu_down_prep(unsigned int cpu) { - cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu)); + disable_delayed_work_sync(&per_cpu(vmstat_work, cpu)); return 0; }