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 4ABD41991B6; Tue, 16 Dec 2025 12:00:28 +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=1765886428; cv=none; b=D1IryPxDGWIssjMNM2VpAi3lDmbQOmU0W0fX/OK/C37S+L7umKJtygV46z2L4vbGPUlSmwAQaEI54ct/Np9zr21az6MKeyH0j+vzmFCQ4/3sPq2cAmhO2/YYhlMAwbV5AjIKyy/MFkIEEQMke/qc3SBUW4MayA55ESQzZJS+uPU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765886428; c=relaxed/simple; bh=kvvWt6GuhVzw8fzTPQMJG9qYxIhrHvcKZrWjN+Alwiw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rNxXEod0JJXphc8Ttb9ZFe/2t6Jpe2A2ZFBIMCcGL+LsEXz/Nr/PS7F0fXsyYLpA8FTpWN4ln15qiKyfMGWEeDgg7/XwXavGJ7VfaE0eGKnxueuMIKlfuqxFI/jMbGmN0M/CAjh0wJFGkARb2luxnA/DQMH6R6ZVL1q2kliFkfU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=dtWhnpuX; 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="dtWhnpuX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69AD2C4CEF1; Tue, 16 Dec 2025 12:00:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1765886427; bh=kvvWt6GuhVzw8fzTPQMJG9qYxIhrHvcKZrWjN+Alwiw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dtWhnpuXwXZhCDLhMSWmFrpmGCrlNNT0F3ExvK1/expjbiUfhsz+tGOm2BGRObfDK FqYK/M31dRP6hBThIpAFpESCqJH1+7l8mWYbonWlHJoDkyNbaUL1HFn7QTd9VSwBwm 5uP30nRJfYMFK8GKa1TeIagvl/m2iLCf9vfncjNU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, K Prateek Nayak , John Stultz , Ingo Molnar , Haiyue Wang , Johannes Weiner , Sasha Levin Subject: [PATCH 6.17 434/507] sched/core: Fix psi_dequeue() for Proxy Execution Date: Tue, 16 Dec 2025 12:14:35 +0100 Message-ID: <20251216111401.181915087@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251216111345.522190956@linuxfoundation.org> References: <20251216111345.522190956@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 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: John Stultz [ Upstream commit c2ae8b0df2d1bb7a063f9e356e4e9a06cd4afe11 ] Currently, if the sleep flag is set, psi_dequeue() doesn't change any of the psi_flags. This is because psi_task_switch() will clear TSK_ONCPU as well as other potential flags (TSK_RUNNING), and the assumption is that a voluntary sleep always consists of a task being dequeued followed shortly there after with a psi_sched_switch() call. Proxy Execution changes this expectation, as mutex-blocked tasks that would normally sleep stay on the runqueue. But in the case where the mutex-owning task goes to sleep, or the owner is on a remote cpu, we will then deactivate the blocked task shortly after. In that situation, the mutex-blocked task will have had its TSK_ONCPU cleared when it was switched off the cpu, but it will stay TSK_RUNNING. Then if we later dequeue it (as currently done if we hit a case find_proxy_task() can't yet handle, such as the case of the owner being on another rq or a sleeping owner) psi_dequeue() won't change any state (leaving it TSK_RUNNING), as it incorrectly expects a psi_task_switch() call to immediately follow. Later on when the task get woken/re-enqueued, and psi_flags are set for TSK_RUNNING, we hit an error as the task is already TSK_RUNNING: psi: inconsistent task state! task=188:kworker/28:0 cpu=28 psi_flags=4 clear=0 set=4 To resolve this, extend the logic in psi_dequeue() so that if the sleep flag is set, we also check if psi_flags have TSK_ONCPU set (meaning the psi_task_switch is imminent) before we do the shortcut return. If TSK_ONCPU is not set, that means we've already switched away, and this psi_dequeue call needs to clear the flags. Fixes: be41bde4c3a8 ("sched: Add an initial sketch of the find_proxy_task() function") Reported-by: K Prateek Nayak Signed-off-by: John Stultz Signed-off-by: Ingo Molnar Tested-by: K Prateek Nayak Tested-by: Haiyue Wang Acked-by: Johannes Weiner Link: https://patch.msgid.link/20251205012721.756394-1-jstultz@google.com Closes: https://lore.kernel.org/lkml/20251117185550.365156-1-kprateek.nayak@amd.com/ Signed-off-by: Sasha Levin --- kernel/sched/stats.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h index 26f3fd4d34cea..73bd6bca4d310 100644 --- a/kernel/sched/stats.h +++ b/kernel/sched/stats.h @@ -180,8 +180,13 @@ static inline void psi_dequeue(struct task_struct *p, int flags) * avoid walking all ancestors twice, psi_task_switch() handles * TSK_RUNNING and TSK_IOWAIT for us when it moves TSK_ONCPU. * Do nothing here. + * + * In the SCHED_PROXY_EXECUTION case we may do sleeping + * dequeues that are not followed by a task switch, so check + * TSK_ONCPU is set to ensure the task switch is imminent. + * Otherwise clear the flags as usual. */ - if (flags & DEQUEUE_SLEEP) + if ((flags & DEQUEUE_SLEEP) && (p->psi_flags & TSK_ONCPU)) return; /* -- 2.51.0