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 C5F5D1ADC7E for ; Thu, 30 Oct 2025 00:19:10 +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=1761783552; cv=none; b=rHVSBikXCgbEoXKKpc78YpWEn4ky42HAcTa/4lWbGheH+hJkCXsKVHk4JGWnZq/ObTUldKRpVwb3fxO965/OC2+KpM2zdUisJR5lhDxjy5fiXWiWNlxOFvkcNW60rYzuRMr4yrbJeLPgqgqQz8cSeVc9dVsXL4a2XoHsv9Qe2EE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761783552; c=relaxed/simple; bh=g+QujWJnUwHRhuZe5J7seS3AUGCqreuCnAqkj/1MMkc=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=N8vxROfJMxVEEuYaWNUBMbXGfwjqfD1lU+DyN8wyKc2snhM39AxvMhi5N3S4mbWpfKULaPy0ElvSReSc2NC385Zb6j0116TM/w3RJBSmZ3ik9/mmJtZKi6EbpzXVHNk4c/hP/weePi+SIQBsObOLOLbmfb18PstvXo9mI3et1pk= 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=0u05ljFc; 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="0u05ljFc" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-3403e994649so825487a91.3 for ; Wed, 29 Oct 2025 17:19:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1761783550; x=1762388350; 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=JqycFpEo/ajRT9W2GQLxpqJNtH5rJBZEesAjfi64RXc=; b=0u05ljFcTW8ewrDCoj4pfwUKG7JTgRH+NwlXN6fVhyCKyBqAWq46dADtcgkS2t04P0 4sleK5i9tvqvxDkWngfyiapKA0Yacxvq/vw71+oMGDRe4XbL42tAvVgyvRaNLqbGFaJy qOQWA1rZmLzWqLfroIaoB53WjF1knPchxwvvCtjZ632+aitAZqgN2rvqqNmgVLzQdFNw zBKLtTL9IiqnYr0Jd5lU5wIXUfvS8BIKk9aQubA+dgku7bzrMU/+NlOKiUn5xJlob4yq Lbawr1wOifDyAmL9rKgwJNDXxNKJ2ELrbfstHXf43FCpO/mA7lFjiK6wGPyDV1CnkP10 YOAw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761783550; x=1762388350; 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=JqycFpEo/ajRT9W2GQLxpqJNtH5rJBZEesAjfi64RXc=; b=Rj89//g59VDU67sEZICxKPdJ6vdRJAjKdpsAQBRoVIsHRm+UcbOS2AsGE/2nnES7EW Vun9OT1YmG0w2+j2MKtsyn9yPrzONeSMBWzWhX/Hqa9ZYIxp8OlHeqPnV1+3Sh2ZjVeF 5zi4uFZzSYgq+YfXWrCJLmXiTMSfhCPVjrfT3scJfpHiHrFYZyI9qJnnxpF/fLfLgFXD ajG01VQnwdK4KRNWiMZMMueLQA11A3ICCI/s4M2hhP0FD4Lt82YkM+n3WG8JLbqz305V IpJtHjyLjPGnD+yl8en23bl2vxjPJit/IrvmVZIdCul4i+2ZMmUoh7cTU2VS6iq2N5i6 Q38w== X-Gm-Message-State: AOJu0Yx9oOZ3h75dAnGU4JkOiFyU8JeNU/+3ybY9JFwE4HbfVzIWy1n2 4C3xH0iRCI4+1XEmaA4XVvLc7tW+mv4s4QjQG82KctplVXyulqPyzj54y3MAE9211bqnBuIbuhd jcjviW5UHwxSIEFHgHBcPoQPUE8qv5w86IunzAXEYiuuB/XTFB2r1xAKwIgpsF04YQ5daeWRSvW UpfVqBnss6hlbGBBYt3rZPXEQ/AcwvpAcMz7k3ffJndeC+7Jna X-Google-Smtp-Source: AGHT+IEXoNXvskRxfAbogtvPYzzCEwDJ/L6nfcxEd1zZm3+NJqeAnn6dI3CviE/FdnVtHYXBG79vkPCqqdHH X-Received: from pjyq10.prod.google.com ([2002:a17:90a:e08a:b0:33b:51fe:1a88]) (user=jstultz job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:3811:b0:330:6d5e:f174 with SMTP id 98e67ed59e1d1-3403a2a3438mr5495416a91.20.1761783550119; Wed, 29 Oct 2025 17:19:10 -0700 (PDT) Date: Thu, 30 Oct 2025 00:18:46 +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: <20251030001857.681432-6-jstultz@google.com> Subject: [PATCH v23 5/9] 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-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 != &balance_push_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 balance 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 v22: * Spelling fix suggested by K Prateek * Collapsed the stub implementation to one line as suggested by K Prateek * Zap callbacks when we resched idle, 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 | 41 +++++++++++++++++++++++++++++++++++++++-- 1 file changed, 39 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 680ff147d270d..ab6e14259bdf2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4970,6 +4970,38 @@ static inline void finish_task(struct task_struct *prev) smp_store_release(&prev->on_cpu, 0); } +#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 = false; + + lockdep_assert_rq_held(rq); + + head = rq->balance_callback; + while (head) { + if (head == &balance_push_callback) + found = true; + next = head->next; + head->next = NULL; + head = next; + } + rq->balance_callback = 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 *head) { void (*func)(struct rq *rq); @@ -6901,10 +6933,15 @@ static void __sched notrace __schedule(int sched_mode) rq_set_donor(rq, next); if (unlikely(task_is_blocked(next))) { next = 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 == rq->idle) + } + if (next == rq->idle) { + zap_balance_callbacks(rq); goto keep_resched; + } } picked: clear_tsk_need_resched(prev); -- 2.51.1.930.gacf6e81ea2-goog