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 B8E3A14F98; Sat, 9 Aug 2025 19:05:58 +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=1754766358; cv=none; b=BePcN/l8CGgIIOqJkVaH8L/hxo2Wgn5FEVMiNupqz+gMlwTCr20UuZ8qN30eT0H1TmVobGXSRMxgCDYPTFjLVPvSLna7ctuS76EiJpTm3Y69/UkOyB5AfnabOdbVsqrwnLXDKw/VdBYTxCWW8jukuKed304/xaxJUb0aG8SR7Y8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754766358; c=relaxed/simple; bh=rExTbwvEF3xB6jxB/Z8+HO6SeihUoUr7IJLIc0lvJwU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=f0L5rbZmwhv1YqJhnePAGWb7+0519KKCCsXClmNr9qN5bCVmA2ERHHWaUyrhCnHByxDQDC3oqvx2A3SGsvkIlKgIVj+RSizWfSzUY6aU+d+6DSVgJwwfIYXmub+0dlE2MfM6jEprJZGFEgiBcBqiw1wQGNnXyW0ha5u1zyCq/d0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WbjmDOkk; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WbjmDOkk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A1DCC4CEE7; Sat, 9 Aug 2025 19:05:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754766358; bh=rExTbwvEF3xB6jxB/Z8+HO6SeihUoUr7IJLIc0lvJwU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WbjmDOkkVGFCuG2g+0VLhqtvdOjRHyx6BEk6ux9V5W+CTu3zhCa4VBvUmMPHA5jcx g85uvST3LMXA4XS/WLzrHPcshfhZM0owuvn9OsN7fkBuvk0HXfUmCUMKpr6vMtG9wK Flz4Jbo1ER3j47OyMed8zCx+V3OCkQlMrzSS+qDkUMMuK9XdmTW3qjF2zLfkPS5kzP uqyosO82QAz5VAR4FKDW34AgnlYqoUvCZLIEBPy27/tajzgDfMACMuL60eUoRKY7JS 8tNIGLjvcpH/ZJUB/tFKSWOBvK0wHZ/FjhBa+5AIjztx3p+rJA/tn5QtkkZNhIUK8Q D6n7prAxmj3gg== Date: Sat, 9 Aug 2025 09:05:57 -1000 From: Tejun Heo To: Andrea Righi Cc: David Vernet , Changwoo Min , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched/ext: Fix invalid task state transitions on class switch Message-ID: References: <20250805085911.164956-1-arighi@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250805085911.164956-1-arighi@nvidia.com> On Tue, Aug 05, 2025 at 10:59:11AM +0200, Andrea Righi wrote: > When enabling a sched_ext scheduler, we may trigger invalid task state > transitions, resulting in warnings like the following (which can be > easily reproduced by running the hotplug selftest in a loop): > > sched_ext: Invalid task state transition 0 -> 3 for fish[770] > WARNING: CPU: 18 PID: 787 at kernel/sched/ext.c:3862 scx_set_task_state+0x7c/0xc0 > ... > RIP: 0010:scx_set_task_state+0x7c/0xc0 > ... > Call Trace: > > scx_enable_task+0x11f/0x2e0 > switching_to_scx+0x24/0x110 > scx_enable.isra.0+0xd14/0x13d0 > bpf_struct_ops_link_create+0x136/0x1a0 > __sys_bpf+0x1edd/0x2c30 > __x64_sys_bpf+0x21/0x30 > do_syscall_64+0xbb/0x370 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > This happens because we skip initialization for tasks that are already > dead (with their usage counter set to zero), but we don't exclude them > during the scheduling class transition phase. > > Fix this by also skipping dead tasks during class swiching, preventing > invalid task state transitions. > > Fixes: a8532fac7b5d2 ("sched_ext: TASK_DEAD tasks must be switched into SCX on ops_enable") > Signed-off-by: Andrea Righi Applied to sched_ext/for-6.17-fixes. Thanks. -- tejun