From nobody Mon Oct 6 13:37:48 2025 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (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 53BAF2C08B6 for ; Tue, 22 Jul 2025 07:06:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753167989; cv=none; b=VUdH8D9iOB51hBqRyzwPoxnQ34226FvEWFMgKK/apr+sVp4sS4QyvYSKefpvQogRVVAddFNDust2wHIhSDYnKUAR7cuZFZ52tRZqzDdxqRBpUInFWkceOVVlHGRP4VN+W+uPi8fB5qo6QUcWQGFkTF/MqsdaM0/kyxLP6sQDZ2M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753167989; c=relaxed/simple; bh=upFUszo1X4k/1v3kcSQhzPWQiLwPemqlypvnvLUec9o=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Xdvz1ondjLy9QJCmhx+OwBV0isx/u2ukjQPkhikdJ4m+i6mrTbOc+yBAAG+f8cS93Qbu1cPE9l9wdoPgBzN/q1C0ZTmY3XNd4qxtw1pryqH61lW10doUE5JOk6PewuG+WPQUp99ec9SKg+d9b+kGEnxNlc8/u9UCc+LyG5VT9pI= 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=JjmI90/u; arc=none smtp.client-ip=209.85.214.201 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="JjmI90/u" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-235eefe6a8fso39213255ad.1 for ; Tue, 22 Jul 2025 00:06:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1753167986; x=1753772786; 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=6mcaKefYRF9M4725G07PH0aETmeSusN8vwiT8bvtjZ0=; b=JjmI90/u6QhaglT9pSGJRWJR4NQ/Px1E2S+VWUP72cCHiJXJILv/anq5v+hPW7rL9U 5xPACbk88yXNYLmUPZmOjDOPjRgKsVMjhRbwLLTFvICQWQdHdjaDDK0d5WYJ2NEHWb5N hJcF4LZDo9MhOn1AaEhwuI6gnWs4O9iPENeRo+Ec9ydhnKtU8aVQJDkx+t8wMggWUoqX XWUJziNsEhpifPuYOim/iw6a64a31zuDi5KzdnaW19ENnbj+cIV9d45w/JmzRsmhJlVE oR0PyPBKTp1wVkXbGMZCWx9d/Cf5HCqbaLNfcebTfYLuUnqflMwLkIO5IKK/idDe1uFe psjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1753167986; x=1753772786; 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=6mcaKefYRF9M4725G07PH0aETmeSusN8vwiT8bvtjZ0=; b=m45UwtuAQEVufXEyNEwxTaUYxL6wh2so2SdcB5R2819qXjldLb2wX9lGeQFfDXJyS9 4urVDLALBOzNpz4kgRdRgJJcNmFokt2BT5K7rLrIC/Q/adxvhZW3544b0pKu6njFzstz T0ZDRVQjX/mljwsI/d8M1Zh+yC6ho/ZfKAoy104QUFw2blKUEnAbQUcn7Rmf7wzmTxmT /zXDGfvycOVtyoYrr4sfG6xtA6lE8q+YoIR3H4lprY4fBFz8S3bcn9Er6FPq1anY+X0I 97lb54Kc7k5onmHcbrdNKj3M7kmgqMdtIpJbBcYlQl2ETX4qb/XffBzMLm95IeX3Z3tb LIyw== X-Gm-Message-State: AOJu0YxUISznOebFgZqEu6TRKS0J7svYWjW7vTaIcMI0FEsN9m4sUadi 6Vhgbzq5+QhNDfEbyxHCxdmpd7gKoMyU+9V+YXl9MmGJ4ruvj0+3We0OG+tOI9a5GMRVqQLGqqL ngiRUCU+3Mj4B4RBKrArYXfiNZHYEF9F1LbpOBPzIOoNruTQBn2EUiPe45lYH71pDGR8xEHefql W4aVcVu7eUfFx+Q52KVCU9rcEEXfBv75cDkt7dT+YMLnVNXzd6 X-Google-Smtp-Source: AGHT+IEUZiwpCUDJ17os2Y/Rny4HU3K/F+cfRT7oN03A9czTfyDTuS1tCWHOwPySx8wi0OhVDElCD9md2TRV X-Received: from plgb6.prod.google.com ([2002:a17:902:d506:b0:236:369f:dfc9]) (user=jstultz job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:988:b0:234:c22:c612 with SMTP id d9443c01a7336-23e3b84f767mr214122725ad.43.1753167986411; Tue, 22 Jul 2025 00:06:26 -0700 (PDT) Date: Tue, 22 Jul 2025 07:05:49 +0000 In-Reply-To: <20250722070600.3267819-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250722070600.3267819-1-jstultz@google.com> X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog Message-ID: <20250722070600.3267819-4-jstultz@google.com> Subject: [RFC][PATCH v20 3/6] sched: Add logic to zap balance callbacks if we pick again 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-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" With proxy-exec, a task is selected to run via pick_next_task(), and then if it is a mutex blocked task, we call find_proxy_task() to find a runnable owner. If the runnable owner is on another cpu, we will need to migrate the selected donor task away, after which we will pick_again can call pick_next_task() to choose something else. However, in the first call to pick_next_task(), we may have had a balance_callback setup by the class scheduler. After we pick again, its possible pick_next_task_fair() will be called which calls sched_balance_newidle() and sched_balance_rq(). This will throw a warning: [ 8.796467] rq->balance_callback && rq->balance_callback !=3D &balance_p= ush_callback [ 8.796467] WARNING: CPU: 32 PID: 458 at kernel/sched/sched.h:1750 sched= _balance_rq+0xe92/0x1250 ... [ 8.796467] Call Trace: [ 8.796467] [ 8.796467] ? __warn.cold+0xb2/0x14e [ 8.796467] ? sched_balance_rq+0xe92/0x1250 [ 8.796467] ? report_bug+0x107/0x1a0 [ 8.796467] ? handle_bug+0x54/0x90 [ 8.796467] ? exc_invalid_op+0x17/0x70 [ 8.796467] ? asm_exc_invalid_op+0x1a/0x20 [ 8.796467] ? sched_balance_rq+0xe92/0x1250 [ 8.796467] sched_balance_newidle+0x295/0x820 [ 8.796467] pick_next_task_fair+0x51/0x3f0 [ 8.796467] __schedule+0x23a/0x14b0 [ 8.796467] ? lock_release+0x16d/0x2e0 [ 8.796467] schedule+0x3d/0x150 [ 8.796467] worker_thread+0xb5/0x350 [ 8.796467] ? __pfx_worker_thread+0x10/0x10 [ 8.796467] kthread+0xee/0x120 [ 8.796467] ? __pfx_kthread+0x10/0x10 [ 8.796467] ret_from_fork+0x31/0x50 [ 8.796467] ? __pfx_kthread+0x10/0x10 [ 8.796467] ret_from_fork_asm+0x1a/0x30 [ 8.796467] This is because if a RT task was originally picked, it will setup the rq->balance_callback with push_rt_tasks() via set_next_task_rt(). Once the task is migrated away and we pick again, we haven't processed any balance callbacks, so rq->balance_callback is not in the same state as it was the first time pick_next_task was called. To handle this, add a zap_balance_callbacks() helper function which cleans up the blance callbacks without running them. This should be ok, as we are effectively undoing the state set in the first call to pick_next_task(), and when we pick again, the new callback can be configured for the donor task actually selected. Signed-off-by: John Stultz --- v20: * Tweaked to avoid build issues with different configs 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 | 39 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7ae5f2d257eb5..30e676c2d582b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4990,6 +4990,40 @@ static inline void finish_task(struct task_struct *p= rev) smp_store_release(&prev->on_cpu, 0); } =20 +#ifdef CONFIG_SCHED_PROXY_EXEC +/* + * Only called from __schedule context + * + * There are some cases where we are going to re-do the action + * that added the balance callbacks. We may not be in a state + * where we can run them, so just zap them so they can be + * properly re-added on the next time around. This is similar + * handling to running the callbacks, except we just don't call + * them. + */ +static void zap_balance_callbacks(struct rq *rq) +{ + struct balance_callback *next, *head; + bool found =3D false; + + lockdep_assert_rq_held(rq); + + head =3D rq->balance_callback; + while (head) { + if (head =3D=3D &balance_push_callback) + found =3D true; + next =3D head->next; + head->next =3D NULL; + head =3D next; + } + rq->balance_callback =3D found ? &balance_push_callback : NULL; +} +#else +static inline void zap_balance_callbacks(struct rq *rq) +{ +} +#endif + static void do_balance_callbacks(struct rq *rq, struct balance_callback *h= ead) { void (*func)(struct rq *rq); @@ -6920,8 +6954,11 @@ static void __sched notrace __schedule(int sched_mod= e) rq_set_donor(rq, next); if (unlikely(task_is_blocked(next))) { next =3D find_proxy_task(rq, next, &rf); - if (!next) + if (!next) { + /* zap the balance_callbacks before picking again */ + zap_balance_callbacks(rq); goto pick_again; + } if (next =3D=3D rq->idle) goto keep_resched; } --=20 2.50.0.727.gbf7dc18ff4-goog