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 1A3872F290B for ; Mon, 29 Dec 2025 11:36:54 +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=1767008215; cv=none; b=sdRCqdVmEPcyz70pSzD4vgFwxbLsUdND/ZDz5eVSQvnjzSGlM1DC0eL0a5Lx/z3dmorC5ZV8qQqm59qsA6MQkr0UWeehXpcFuNZPsmd1bSvB7aqXRvwidtglMv1qzB5+VoFtPzRwmlqL8wfmZnclgLDLXiFGvhnbzPBjrJUX/94= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767008215; c=relaxed/simple; bh=Zu7ll8M1lf9B31ggRP5CHl7AxseWj7l8mQWGfVgD+V0=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=opzoZx+2FIUTrJf/7TVYCAuKpnCErfiqADeeHLoalfAqUdn4icSgOSlHp8GTeGwjvkkOThufLYAFWA3TstDXZsBNuYZR33ONEDmYudcesdr2H5TB61SNdhNUwlYOGDoczDp6K8OBU1OjbkffGBnJ7sfioaFDIHUqy253TXSN4U0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qQ+WZA/Y; 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="qQ+WZA/Y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 607E7C4CEF7; Mon, 29 Dec 2025 11:36:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767008213; bh=Zu7ll8M1lf9B31ggRP5CHl7AxseWj7l8mQWGfVgD+V0=; h=Subject:To:Cc:From:Date:From; b=qQ+WZA/Yy8Zg9uxD2Q1PFCwYwPHecoNL1P6aomZUriRFtd6YAb1IT7pEmepwe5P+x 28RZqdTE16ZuoZ1q7CvfY3tUp6BV0Za1hOIFf0XAFHapSHp7oaBRb3WosTRSe9Z7w1 T8NxSiXcU/dOPB8bu/DYd0zjKJUgRVpuJMEkThWQ= Subject: FAILED: patch "[PATCH] sched_ext: Fix missing post-enqueue handling in" failed to apply to 6.12-stable tree To: tj@kernel.org,arighi@nvidia.com,emil@etsalapatis.com Cc: From: Date: Mon, 29 Dec 2025 12:36:51 +0100 Message-ID: <2025122951-giggle-reveler-2e6b@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x f5e1e5ec204da11fa87fdf006d451d80ce06e118 # git commit -s git send-email --to '' --in-reply-to '2025122951-giggle-reveler-2e6b@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From f5e1e5ec204da11fa87fdf006d451d80ce06e118 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 11 Dec 2025 15:45:04 -1000 Subject: [PATCH] sched_ext: Fix missing post-enqueue handling in move_local_task_to_local_dsq() move_local_task_to_local_dsq() is used when moving a task from a non-local DSQ to a local DSQ on the same CPU. It directly manipulates the local DSQ without going through dispatch_enqueue() and was missing the post-enqueue handling that triggers preemption when SCX_ENQ_PREEMPT is set or the idle task is running. The function is used by move_task_between_dsqs() which backs scx_bpf_dsq_move() and may be called while the CPU is busy. Add local_dsq_post_enq() call to move_local_task_to_local_dsq(). As the dispatch path doesn't need post-enqueue handling, add SCX_RQ_IN_BALANCE early exit to keep consume_dispatch_q() behavior unchanged and avoid triggering unnecessary resched when scx_bpf_dsq_move() is used from the dispatch path. Fixes: 4c30f5ce4f7a ("sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()") Cc: stable@vger.kernel.org # v6.12+ Reviewed-by: Andrea Righi Reviewed-by: Emil Tsalapatis Signed-off-by: Tejun Heo diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index c78efa99406f..695503a2f7d1 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -988,6 +988,14 @@ static void local_dsq_post_enq(struct scx_dispatch_q *dsq, struct task_struct *p struct rq *rq = container_of(dsq, struct rq, scx.local_dsq); bool preempt = false; + /* + * If @rq is in balance, the CPU is already vacant and looking for the + * next task to run. No need to preempt or trigger resched after moving + * @p into its local DSQ. + */ + if (rq->scx.flags & SCX_RQ_IN_BALANCE) + return; + if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr && rq->curr->sched_class == &ext_sched_class) { rq->curr->scx.slice = 0; @@ -1636,6 +1644,8 @@ static void move_local_task_to_local_dsq(struct task_struct *p, u64 enq_flags, dsq_mod_nr(dst_dsq, 1); p->scx.dsq = dst_dsq; + + local_dsq_post_enq(dst_dsq, p, enq_flags); } /**