From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.128.70 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792766921; b=3/0O6SVcBYXBlKX2iApV2VZ37FvzpS4nm/2eOS7WFa9v70H3VGac61AIuR3sQFKyCPr+ gZWoIIgEJYv+Gfrbk11SMTNBb6KikxjPlaPKSFXRB5c0V5wA00mIjLTigD76YqenvLTji Rlrf0BnOoUZf4zzi2/4FwSqL2nr1gyzBlJFRHG1tvCRqL3Wugzkiy9gktFjoMB/6O0Cdp qYNz2/Avz7AVfTbO4au3JOvefHuEZYVCIJthTTdX9bm7sRVZYjcuusUyJ3coQroucZdXv ESGac1bME4C9LJ6MAfZnRnRjPwPCDiKht5L9Q3L7q52S18Abx7rpZehqwgrqZkxxJHw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792766921; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Received:Date:In-Reply-To: Mime-Version:References:X-Mailer:Message-ID:Subject:From:To:Cc: Content-Type; bh=XoNiU9ULidIP7mhpM0I3d1L1MqWC9duVSz+nVIzIlO4=; b=p1mV9/tHHN7332rhy1X30clUp7pqCsceOKGi3Xe3bpCj4QqpvAmTsnRO1ybIuAhyJYX9 ljql7Mojz0os7pTEInMMkKBm2ZDiQ1Bu8S6uiylEMJWEVL3CJ/GEd4U+S4dnY9fp50KiT UMFr6F2AAzxxj8+NcZ8pkot/vMBfwRh/03+EJ2fjBqn4hSMRptmDsfhU4DRuSwlscOfYE OQulimFIbgya3eUpQlQfF6BrEsJDKB2zGbwkd/0WXzfzX7BY998U3/KqtV/zyk/i1JTar mion4/UyOGDTxUzW2k9/wH1xqky9Zkd7MmhIDVKSy8F4/Sx8n/fdKw39scnH0cI6vEg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=google.com; spf=pass smtp.mailfrom=flex--jpiecuch.bounces.google.com; dkim=pass header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20251104 header.b=t2mtBxPK; arc=none smtp.remote-ip=209.85.128.70 Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5C159606A31A for ; Fri, 23 Oct 2026 14:48:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 5C159606A31A Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jpiecuch.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20251104 header.b=t2mtBxPK Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-4a20fd059ddso7623745e9.0 for ; Fri, 23 Oct 2026 07:48:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1792766919; x=1793371719; darn=lists.linux.dev; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=XoNiU9ULidIP7mhpM0I3d1L1MqWC9duVSz+nVIzIlO4=; b=t2mtBxPKkLJT0OQfNx0e7W5EwX/mjWFXluHvo63UO0fsNImuI6u8Fr+WmnboFNGLoW 9XzFGxy93gIUkTRyhm3MQ2hvyp4xDoCFMekDFkj7i/1lCogPYYjSKctauGNMsDnCmyfe dtmCPsHDgs1iNSlBeh+NLobltGmQJnL74XjrCoBSk0dMzpLS0nLkMoAo7tGGOCZSDUJI 52YM8DCDuS/3jV1v9ShLyvoPNK/BawcFn04uno8MKgGi6Gt723q8kwrIvw2UlpYGmI06 pZfRSIiQl0wAQD0/sFreGtMhTJ/TOugb3ExSTSBlblr4sdIH9kASTo5JqIxehW2EeKSX oMCg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792766919; x=1793371719; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=XoNiU9ULidIP7mhpM0I3d1L1MqWC9duVSz+nVIzIlO4=; b=DYWRkGJVPwW3D9BBftuF++ZCbqRjlcUTG/s4tU5B06Om9sCKJ6FFHK5mxMnacQLAL0 3o/wSPqsq3jYmB5CzEHsBHKDwLCjh0fQadbOE1HjZbyFEc1pvVxbKwrXuMviWsli7hmS nLrlsyKc+s01Nk0Op6d1FE/dJCBXo3O0WHy5/QyZN0+V538N73u1g9fO1hjooYnI51qu jYDnRRMelaSiiLxTB4dtoAPJ5R6gnovK7LhBE1lPXDKBTeal33V6HHN/2J12a49kd4SA 2mXeAO6rbNEaL0QWGhilj3kfMlWrzXqimU/shjGiWRFY+kSh9nDcyOX0XD9meNjLm430 /u4g== X-Forwarded-Encrypted: i=1; AKwUvBy3dzVTEc1IyoFq7KT9EWb5DcUKyqrGWJZOTeCgpFwWBgJTmzU4Hk7rQ7gwtxXpxOm9je/WbdzXvz8=@lists.linux.dev X-Gm-Message-State: AFq9FYKbISCD6KIHa7pVT6iB6zuJwcOdW/egGW9I2oUFx1l+AzFp1G1h KhY7inDTWJAgYcH9AamK9URLWQiqg8nGXi06Vs39qeLPQTZ5e3fx2mFdB3zqD2hxEjrWR04PDKa UnjVkWywUZXK2gQ== X-Received: from wmoo14.prod.google.com ([2002:a05:600d:10e:b0:4a1:df53:c6c2]) (user=jpiecuch job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:a00c:b0:4a1:e6c8:ff74 with SMTP id 5b1f17b1804b1-4a211f11bf8mr35857445e9.29.1792766918592; Fri, 23 Oct 2026 07:48:38 -0700 (PDT) Date: Fri, 23 Oct 2026 14:48:04 +0000 In-Reply-To: <20261023144811.2230393-1-jpiecuch@google.com> X-Mailing-List: sched-ext@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 References: <20261023144811.2230393-1-jpiecuch@google.com> X-Mailer: git-send-email 2.56.0.257.gf7497c7d27-goog Message-ID: <20261023144811.2230393-2-jpiecuch@google.com> Subject: [PATCH 1/2] sched/core: Preserve WF_RQ_SELECTED across queued wakeups From: Kuba Piecuch To: Tejun Heo , Peter Zijlstra Cc: Kuba Piecuch , David Vernet , Andrea Righi , Changwoo Min , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" ENQUEUE_RQ_SELECTED tells a sched_class that ->select_task_rq() was called for a task wakeup. sched_ext exposes this flag to BPF schedulers as SCX_ENQ_CPU_SELECTED. However, the flag is lost for queued wakeups, which a BPF scheduler can opt into with SCX_OPS_ALLOW_QUEUED_WAKEUP. This also results in undercounting SCX_EV_SELECT_CPU_FALLBACK events. Preserve WF_RQ_SELECTED for queued wakeups in the same way WF_MIGRATED is. This way, ttwu_activate() receives WF_RQ_SELECTED for queued wakeups and passes ENQUEUE_RQ_SELECTED to activate_task(). Fixes: 3539c6411a7c ("sched_ext: Implement SCX_OPS_ALLOW_QUEUED_WAKEUP") Signed-off-by: Kuba Piecuch --- include/linux/sched.h | 6 ++++-- kernel/sched/core.c | 10 +++++++++- 2 files changed, 13 insertions(+), 3 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 12a7e094a3e6..9dabffea1c54 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1006,7 +1006,7 @@ struct task_struct { /* Unserialized, strictly 'current' */ /* - * This field must not be in the scheduler word above due to wakelist + * These fields must not be in the scheduler word above due to wakelist * queueing no longer being serialized by p->on_cpu. However: * * p->XXX = X; ttwu() @@ -1016,9 +1016,11 @@ struct task_struct { * p->on_rq = 0; p->sched_remote_wakeup = Y; * * guarantees all stores of 'current' are visible before - * ->sched_remote_wakeup gets used, so it can be in this word. + * ->sched_remote_wakeup and ->sched_rq_selected get used, so they can + * be in this word. */ unsigned sched_remote_wakeup:1; + unsigned sched_rq_selected:1; #ifdef CONFIG_RT_MUTEXES unsigned sched_rt_mutex:1; #endif diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0ab15f03cb94..d8495735166d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3975,13 +3975,20 @@ void sched_ttwu_pending(void *arg) update_rq_clock(rq); llist_for_each_entry_safe(p, t, llist, wake_entry.llist) { + int wake_flags = 0; + if (WARN_ON_ONCE(p->on_cpu)) smp_cond_load_acquire(&p->on_cpu, !VAL); if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq))) set_task_cpu(p, cpu_of(rq)); - ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf); + if (p->sched_remote_wakeup) + wake_flags |= WF_MIGRATED; + if (p->sched_rq_selected) + wake_flags |= WF_RQ_SELECTED; + + ttwu_do_activate(rq, p, wake_flags, &rf); } /* @@ -4025,6 +4032,7 @@ static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags struct rq *rq = cpu_rq(cpu); p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED); + p->sched_rq_selected = !!(wake_flags & WF_RQ_SELECTED); WRITE_ONCE(rq->ttwu_pending, 1); #ifdef CONFIG_SMP -- 2.56.0.257.gf7497c7d27-goog