From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC2B1350A3C; Tue, 21 Oct 2025 20:02:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761076933; cv=none; b=WtMWsaABd4hdV/LlL3Nv2KjaBlhyryXAkKxYQ7wBeNIdiIliBdYX92OgGkZt86CqHQTj+qxaCMzDa0+ycuPDI5bddwP/TCtnMiSzwXOk6QYdcb78Gy0rHy9013QBjqiKCeop3x7aDqUD+ZJf/U6bgITv7KmKF9m8pcLSAnIYfe0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761076933; c=relaxed/simple; bh=evImX3301NFovwySkLTcIayrlHv06j4vI0K3Dhro75I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UCMlLM+40YM76aTYa8W7ZKY2B0AabGnyQ6gA+Zs+IJkFHB0CK1UIvgr93APad1NCp0wRCQkG0ECfL43ZvFKwi5bQ2eiXfoaw54LUl/oab8BlNKwUa2hSSoIyzleTrE+Txk3fGKzu9NYVtawJzq4uPyedaDiVXNvRmXYNS7kC6K4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=yeqblKgM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="yeqblKgM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 792EBC4CEF1; Tue, 21 Oct 2025 20:02:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1761076932; bh=evImX3301NFovwySkLTcIayrlHv06j4vI0K3Dhro75I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yeqblKgMHxeLW/JH+3FjjmgxVxlbS7SGjlK/PLbrdyRcznxt/6jqqcKFCBQ7RkvjA ouoB6SL30nwgnSJQyJXgF+RFk3hY4b492I+mqQyz71lPgdISFY08rP4ku6ty1XKNYd go4hXfzEFrX3ZrBT1laytcXfGDbiTwKHANHRtFqY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vincent Guittot , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 6.12 082/136] sched/fair: Fix pelt lost idle time detection Date: Tue, 21 Oct 2025 21:51:10 +0200 Message-ID: <20251021195037.937834626@linuxfoundation.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251021195035.953989698@linuxfoundation.org> References: <20251021195035.953989698@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vincent Guittot [ Upstream commit 17e3e88ed0b6318fde0d1c14df1a804711cab1b5 ] The check for some lost idle pelt time should be always done when pick_next_task_fair() fails to pick a task and not only when we call it from the fair fast-path. The case happens when the last running task on rq is a RT or DL task. When the latter goes to sleep and the /Sum of util_sum of the rq is at the max value, we don't account the lost of idle time whereas we should. Fixes: 67692435c411 ("sched: Rework pick_next_task() slow-path") Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Sasha Levin --- kernel/sched/fair.c | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index b3d9826e25b03..8bdcb5df0d461 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9059,21 +9059,21 @@ pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf return p; idle: - if (!rf) - return NULL; - - new_tasks = sched_balance_newidle(rq, rf); + if (rf) { + new_tasks = sched_balance_newidle(rq, rf); - /* - * Because sched_balance_newidle() releases (and re-acquires) rq->lock, it is - * possible for any higher priority task to appear. In that case we - * must re-start the pick_next_entity() loop. - */ - if (new_tasks < 0) - return RETRY_TASK; + /* + * Because sched_balance_newidle() releases (and re-acquires) + * rq->lock, it is possible for any higher priority task to + * appear. In that case we must re-start the pick_next_entity() + * loop. + */ + if (new_tasks < 0) + return RETRY_TASK; - if (new_tasks > 0) - goto again; + if (new_tasks > 0) + goto again; + } /* * rq is about to be idle, check if we need to update the -- 2.51.0