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Fri, 06 Mar 2026 04:49:14 -0800 (PST) Received: from mi-HP-ProDesk-680-G6-PCI-Microtower-PC.mioffice.cn ([43.224.245.226]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ae83e78f77sm27712845ad.21.2026.03.06.04.49.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Mar 2026 04:49:13 -0800 (PST) From: zhidao su X-Google-Original-From: zhidao su To: tj@kernel.org, sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org Cc: void@manifault.com, arighi@nvidia.com, changwoo@igalia.com, linux-kselftest@vger.kernel.org, Su Zhidao Subject: [PATCH 3/5] sched_ext: Use rcu_dereference_bh() in scx_bypass_lb_timerfn() Date: Fri, 6 Mar 2026 20:48:59 +0800 Message-ID: <20260306124901.2653465-3-suzhidao@xiaomi.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Su Zhidao scx_bypass_lb_timerfn() runs in softirq (BH) context, so rcu_dereference_bh() is the correct RCU accessor. The previous rcu_dereference_all() suppresses all sparse warnings and masks potential RCU context issues. Add a comment noting this is a transitional state: when multi-scheduler support lands, the bypass LB timer will become per-scheduler and the global scx_root reference will be removed. Signed-off-by: Su Zhidao --- kernel/sched/ext.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 053d99c58802..c269e489902c 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4170,7 +4170,13 @@ static void scx_bypass_lb_timerfn(struct timer_list *timer) int node; u32 intv_us; - sch = rcu_dereference_all(scx_root); + /* + * scx_bypass_lb_timer is a global timer that fires in softirq + * context while bypass mode is active. Use rcu_dereference_bh() + * matching the BH context. When multi-scheduler support lands, + * this timer will become per-scheduler instance. + */ + sch = rcu_dereference_bh(scx_root); if (unlikely(!sch) || !READ_ONCE(scx_bypass_depth)) return; -- 2.43.0