From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83A021C84C6 for ; Thu, 30 Oct 2025 00:19:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761783548; cv=none; b=T0+DMe5pNTyLqnyOyMgTJwsob30qyOJn7R99ecE/j8RE1noVtMTGBvU2vOWYsGFfRF/DDcR2SPn3RYmhgGrFJ5RGobmz7bySBYeYzKinYqRAeY/VeHNdw2I7Xiuvu5S5CzM2BISPKJrj1vWqC6o32iW2/p2McNp9lOICZDEONM4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761783548; c=relaxed/simple; bh=4lKVWMzCVAA+UKev1Y/i+yoP3fT7r+NXsqiPCaMN3lc=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=dP/bzOyk2b7IybI0caHH83XJTSjlghvrzan3v0/6x+jldnH/hdvJZh5SaCPJhrx0cf43+C0FhkF3PUkc7t/IsEyDHU5EradfucaqITRjzEKsQr8XSugerS+Y8lFTSNlOHi8BoSFVvQ5Zyd4wOOCEcfibtXzEkDtv4e5nEt7TgRY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=EGk3xee5; arc=none smtp.client-ip=209.85.216.73 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--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="EGk3xee5" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-33428befc08so962101a91.2 for ; Wed, 29 Oct 2025 17:19:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1761783546; x=1762388346; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=3VbL2RLeOjLSUJQM2/KV7qhgh5vfmiQYmlgBlL4D9dM=; b=EGk3xee5J43B3C9oschtIjFyWGF5jLrh6Yhi9328YYYV55OJPpQFOIFKhcdFJNdaFf KKCoiEViIHU5E7OUsHLDZL0R5eeSiyUqYVeWnOlqsv02XEFgjSSwdV2q9hJSwpOd5Ghr eenADrwIkGlO49ficckSHQmBoP17HvSpsUqvoJukrSpXEarVrd056darpM1+l3Tm5tf5 UxjPjNhfrq/zSXuKZ4mnYf3K3qSTr2efo8gTKuqZZ+H6z7RqE+MoXoDwev5ld9Ojc2wT W23YcDjZ02PlVAREeIjuqW7hwE2CiVbjLA15VUYMHv5fdtLWiV6p9fzzOJMBDXLYgkqm YDIA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761783546; x=1762388346; h=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; bh=3VbL2RLeOjLSUJQM2/KV7qhgh5vfmiQYmlgBlL4D9dM=; b=BHq5IG17jSoOXqmqfU4liITpOVq7UX4W7x3c2WrYq08I37Hgx0ivnUgKnylmHhWB7p VnsxCPXGV1msaPr6yO+lGbWUNLBygfKpc8hGkJ8mHLIdft/gy2DD5f9ls2q2maudlmIA WW2bA9B8iJC1b9XFK0mwIyTAIWwjBYKA1swJe0xGIPe5zAyGq3Qtc7rqrJOx1KabOj9E s8MrOgnRVLxo4R+TkxE53q0FlbTY80ofKDs6u/qVNq4ZXLx62DbAmpMu+IyTjGjsvF7U QQCcS+RLiGEpLAaoi7+IAlsAveJrfYqpppwc4uRf9xdCZBjvuPshAmISmioahfwgbNgu lSBg== X-Gm-Message-State: AOJu0YwXhFaJqVeaZWfs+WrA0v9Tn7X6/gwxg7B1FgIti5ocGoaxnTOk G6d5Urqu0kH//QRFC1Fst9R/rLR56OJSG23tMN1OlTTONZL+/wHibeeipWUPnNU6l8A/HmDaXbe IFDYhMAbr7b7jBDzAhvv3QUKXyh6gD6Sq2jOicD4TBP8YU9QtMWYa0/03SqQ+Bp4+kgcuhwpSgV KePAkUMbdjydhiNCBvdaQ87+KjBUZI3shLdQHjyjqolXYienv4 X-Google-Smtp-Source: AGHT+IHndj4sC7MtLZlEGmmYsTN8/RXGKmU2AvSH8/rsywj8lj1UvJt6NxKY1lyMEF82tNU0BNzXAYvD+MRB X-Received: from pjrv16.prod.google.com ([2002:a17:90a:bb90:b0:33b:c59f:b015]) (user=jstultz job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:4f44:b0:32d:90c7:c63b with SMTP id 98e67ed59e1d1-3403a2f218amr5354166a91.30.1761783545580; Wed, 29 Oct 2025 17:19:05 -0700 (PDT) Date: Thu, 30 Oct 2025 00:18:43 +0000 In-Reply-To: <20251030001857.681432-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251030001857.681432-1-jstultz@google.com> X-Mailer: git-send-email 2.51.1.930.gacf6e81ea2-goog Message-ID: <20251030001857.681432-3-jstultz@google.com> Subject: [PATCH v23 2/9] sched: Fix modifying donor->blocked on without proper locking From: John Stultz To: LKML Cc: John Stultz , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Mel Gorman , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , Daniel Lezcano , Suleiman Souhlal , kuyo chang , hupu , kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Introduce an action enum in find_proxy_task() which allows us to handle work needed to be done outside the mutex.wait_lock and task.blocked_lock guard scopes. This ensures proper locking when we clear the donor's blocked_on pointer in proxy_deactivate(), and the switch statement will be useful as we add more cases to handle later in this series. Signed-off-by: John Stultz --- v23: * Split out from earlier patch. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Mel Gorman Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: Daniel Lezcano Cc: Suleiman Souhlal Cc: kuyo chang Cc: hupu Cc: kernel-team@android.com --- kernel/sched/core.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 517b26c515bc5..0533a14ce5935 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6591,7 +6591,7 @@ static struct task_struct *proxy_deactivate(struct rq *rq, struct task_struct *d * as unblocked, as we aren't doing proxy-migrations * yet (more logic will be needed then). */ - donor->blocked_on = NULL; + clear_task_blocked_on(donor, NULL); } return NULL; } @@ -6619,6 +6619,7 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) int this_cpu = cpu_of(rq); struct task_struct *p; struct mutex *mutex; + enum { FOUND, DEACTIVATE_DONOR } action = FOUND; /* Follow blocked_on chain. */ for (p = donor; task_is_blocked(p); p = owner) { @@ -6652,12 +6653,14 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) if (!READ_ONCE(owner->on_rq) || owner->se.sched_delayed) { /* XXX Don't handle blocked owners/delayed dequeue yet */ - return proxy_deactivate(rq, donor); + action = DEACTIVATE_DONOR; + break; } if (task_cpu(owner) != this_cpu) { /* XXX Don't handle migrations yet */ - return proxy_deactivate(rq, donor); + action = DEACTIVATE_DONOR; + break; } if (task_on_rq_migrating(owner)) { @@ -6715,6 +6718,13 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) */ } + /* Handle actions we need to do outside of the guard() scope */ + switch (action) { + case DEACTIVATE_DONOR: + return proxy_deactivate(rq, donor); + case FOUND: + /* fallthrough */; + } WARN_ON_ONCE(owner && !owner->on_rq); return owner; } -- 2.51.1.930.gacf6e81ea2-goog