From nobody Tue Dec 2 01:03:57 2025 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 4DBCA33A6E6 for ; Mon, 24 Nov 2025 22:31:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764023479; cv=none; b=B1cLIhc4lagj0L49zzw3k8gRKfOlBEVLUx4CsoxUEcB//kWuIxRs83u9Va7B7UCrrdhv8vmV2+pGy2T3CoezPmHMRf3I5sNVn6z3gY6sWrV5FurkZt10GbVF4L5wK/at1PEPiVQsZdjzradeuhiNmdhyfrvBKNNN5dOSOStn1Uk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764023479; c=relaxed/simple; bh=dnGK1OFM207LHaWvZ5Oah4Dp8Mj3BFxpa0knZS07sp0=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=gWoEsUl71Vo+6QK9vdGN7gn4wZ3+Q0tVMqJrQdjB74SPTxJLptzUxJoQ9371oflb/8RP+YAcnwR/4Kw6OzIv1E2jD8SomtQri7PJUa6bdnGm5wfll2I6EAtdiZrd7eb/3C78j45eclVusjr5Tv65oG7APcNuMMtf6dasVVNMPXU= 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=CmvRcHC0; arc=none smtp.client-ip=209.85.214.202 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="CmvRcHC0" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-2955f0b8895so57337235ad.0 for ; Mon, 24 Nov 2025 14:31:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1764023477; x=1764628277; 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=LfTUlOrLPZLJACCMG7Y2jp93sr5k+VIyEZrY/1E/AgU=; b=CmvRcHC0IDbmbyi1tkQjRFYr1pUQ8a1rJJckQOVcP38Z0vAX6VNLPxIVXTz3qzZYWT lo26WwwAZZdP7iqx2nNaNgMw8NCIUU9DBlvtQYmMWt+s01OKli8OLO69hgvoW1IAieoM FaTfRpi/xPVcNs9RRLuNKc3iUipcn7SvHisaDdCUxIYZBt6C4h/kNeqxc55GPFEQyhPA tgmbOAIAIDzqduVby+C7qOvTmMbeWSLps0vo3LNavNUtiYd+9ZLSWjY2lhFTvPJHKgBM xjHVdYZqYWCIzokCspgnYc4ENDhHJF7gwX8rNren7U/Sq2jt5bwei3QbMuk9U5ZsQGOc LfXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1764023477; x=1764628277; 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=LfTUlOrLPZLJACCMG7Y2jp93sr5k+VIyEZrY/1E/AgU=; b=MlMEhfspBeI1PVMw3k/1RbYp7VZ6OUZZzIxux++lUIcHNHcqy+H3kBAvdev3BIKtbA L8XqaNWjk+N5CI/ZZ50efHMLUWUsGtiFs2kwteukpRZQMEhXk2+iRTz3JPFz1QwEPr4g YFPRZ8WignWTfM8qZX8wndxIl64aE4lEX+sUZBS0Ieuk7spimtqRrxsc7Mpf/IBg9dTe /b3n5SINnVKmf6LwfYI4WzwyWCExihJGjPm8T3s2hX/rkNullnoE6I1gCyXd1E7IAmGW ghiZsmpr0rP3zYquYqiy8Cl2/8Os/o9e+nj5eJodJ+/7XV19A8ADvr0v0XdZPJ58OWqe GGWA== X-Gm-Message-State: AOJu0YyUwgOw0BxWuXwBMpIaWBJgWOoa33S1XdvH1/9Rykyd8loLPtvw NhSCQFq5k5E5RBKMSyPqLRG6KSte6sRmR0VrqtIC32IlwSSMYb0GYSGcBbT5lXXLGRYpDg6vwk0 961aJER9xjF3M/NYAO74+1JSKj6ZvqDjDVgCQqn5wHmfNc/7LqAqGLMiMFef9KfRkka0N66pEqb R6tqjsmHCJyuJOx3Z6SpFLEQGoRwn1/+9MGezHniSJFe7liOv+ X-Google-Smtp-Source: AGHT+IG8KcxAor0xNtwmCMCFrLatnQYElnPM4TdFvMNk0vgCHTregTxOcR4NDY9eN7XxBc7nPMmUqSY0gc+E X-Received: from plgc11.prod.google.com ([2002:a17:902:d48b:b0:29a:1de:14aa]) (user=jstultz job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:98c:b0:299:dc97:a694 with SMTP id d9443c01a7336-29b5e3b86f5mr189472505ad.24.1764023476502; Mon, 24 Nov 2025 14:31:16 -0800 (PST) Date: Mon, 24 Nov 2025 22:30:54 +0000 In-Reply-To: <20251124223111.3616950-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251124223111.3616950-1-jstultz@google.com> X-Mailer: git-send-email 2.52.0.487.g5c8c507ade-goog Message-ID: <20251124223111.3616950-3-jstultz@google.com> Subject: [PATCH v24 02/11] sched: Fix modifying donor->blocked on without proper locking From: John Stultz To: LKML Cc: John Stultz , K Prateek Nayak , 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 , Thomas Gleixner , Daniel Lezcano , Suleiman Souhlal , kuyo chang , hupu , kernel-team@android.com Content-Transfer-Encoding: quoted-printable 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. Reviewed-by: K Prateek Nayak Signed-off-by: John Stultz --- v23: * Split out from earlier patch. v24: * Minor re-ordering local variables to keep with style as suggested by K Prateek 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 b3f9bc20b7e1f..1b6fd173daadd 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 =3D NULL; + clear_task_blocked_on(donor, NULL); } return NULL; } @@ -6615,6 +6615,7 @@ static struct task_struct *proxy_deactivate(struct rq= *rq, struct task_struct *d static struct task_struct * find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags = *rf) { + enum { FOUND, DEACTIVATE_DONOR } action =3D FOUND; struct task_struct *owner =3D NULL; int this_cpu =3D cpu_of(rq); struct task_struct *p; @@ -6652,12 +6653,14 @@ find_proxy_task(struct rq *rq, struct task_struct *= donor, struct rq_flags *rf) =20 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 =3D DEACTIVATE_DONOR; + break; } =20 if (task_cpu(owner) !=3D this_cpu) { /* XXX Don't handle migrations yet */ - return proxy_deactivate(rq, donor); + action =3D DEACTIVATE_DONOR; + break; } =20 if (task_on_rq_migrating(owner)) { @@ -6715,6 +6718,13 @@ find_proxy_task(struct rq *rq, struct task_struct *d= onor, struct rq_flags *rf) */ } =20 + /* 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; } --=20 2.52.0.487.g5c8c507ade-goog