From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 1804944E045; Tue, 16 Jun 2026 16:38:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781627893; cv=none; b=sReQBPZvtvw01GcTnWJZZecLPw5kSU+BCUllXF1U9pwhyircuUjDaYXv/mF3MQJhO3GaMbAVGJcN3dkCbhyOJtZYNhQbWOyPD8UBGUuan6I2brSWw+6wTg6nyVoo4Rr8+Brf/9WJ0ZLBIbrsU0+uVGBgqlFPi2jiBPNS7E28fIM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781627893; c=relaxed/simple; bh=AjB3u7d67bnzwNXT4xzFlpQ+LP2cFmzNWhaSYEBpD3A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UKIGTLYF/llgkA2NliGqrUF5XQLIKMMpJUQTfujOY53zI0KdF1BXCfft4akXjnnLxFSeULX3xjpYl3okCethebl2m+2bhQfy3Q8DkFyMHfE3KiOG/TX18p/WrtMXEyyZN5LNK+QhDbQ/YR0BsNognwScMWGyCeH6OO6gBvxCNqo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=erRkvarT; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="erRkvarT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 19AED1F000E9; Tue, 16 Jun 2026 16:38:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781627892; bh=dp/4VjO1cYdbygV0RZ2CtUzHyQj9eZ+TiTKwi3j3xJw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=erRkvarTEHKx9pauoZ7TF9mf6L1ldeeAeYC1hP2NDdXgyngHjPSkAsAbptFoNBs3n zLWWaHr2F5omm6e5500h7ErTzZHAspM/5Rke7J/TEUY3krkOJ+BlJgyeakXI5VgJBa dkSOXFz9KmcH6oByOorrYUv4ghbfIhAMANYfhW5M= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Bjorn Andersson , Srinivas Kandagatla Subject: [PATCH 6.12 214/261] slimbus: qcom-ngd-ctrl: Avoid ABBA on tx_lock/ctrl->lock Date: Tue, 16 Jun 2026 20:30:52 +0530 Message-ID: <20260616145054.949815886@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145044.869532709@linuxfoundation.org> References: <20260616145044.869532709@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: Bjorn Andersson commit 55f2ea9ff83cc27a85526b14bc9b32f96a08d6ec upstream. During the SSR/PDR down notification the tx_lock is taken with the intent to provide synchronization with active DMA transfers. But during this period qcom_slim_ngd_down() is invoked, which ends up in slim_report_absent(), which takes the slim_controller lock. In multiple other codepaths these two locks are taken in the opposite order (i.e. slim_controller then tx_lock). The result is a lockdep splat, and a possible deadlock: rprocctl/449 is trying to acquire lock: ffff00009793e620 (&ctrl->lock){+.+.}-{4:4}, at: slim_report_absent (drivers/slimbus/core.c:322) slimbus but task is already holding lock: ffff00009793fb50 (&ctrl->tx_lock){+.+.}-{4:4}, at: qcom_slim_ngd_ssr_pdr_notify (drivers/slimbus/qcom-ngd-ctrl.c:1475) slim_qcom_ngd_ctrl which lock already depends on the new lock. Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&ctrl->tx_lock); lock(&ctrl->lock); lock(&ctrl->tx_lock); lock(&ctrl->lock); The assumption is that the comment refers to the desire to not call qcom_slim_ngd_exit_dma() while we have an ongoing DMA TX transaction. But any such transaction is initiated and completed within a single qcom_slim_ngd_xfer_msg(). Prior to calling qcom_slim_ngd_exit_dma() the slim_controller is torn down, all child devices are notified that the slimbus is gone and the child devices are removed. Stop taking the tx_lock in qcom_slim_ngd_ssr_pdr_notify() to avoid the deadlock. Fixes: a899d324863a ("slimbus: qcom-ngd-ctrl: add Sub System Restart support") Cc: stable@vger.kernel.org Signed-off-by: Bjorn Andersson Signed-off-by: Srinivas Kandagatla Link: https://patch.msgid.link/20260530204421.116824-9-srini@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/slimbus/qcom-ngd-ctrl.c | 3 --- 1 file changed, 3 deletions(-) --- a/drivers/slimbus/qcom-ngd-ctrl.c +++ b/drivers/slimbus/qcom-ngd-ctrl.c @@ -1471,15 +1471,12 @@ static int qcom_slim_ngd_ssr_pdr_notify( switch (action) { case QCOM_SSR_BEFORE_SHUTDOWN: case SERVREG_SERVICE_STATE_DOWN: - /* Make sure the last dma xfer is finished */ - mutex_lock(&ctrl->tx_lock); if (ctrl->state != QCOM_SLIM_NGD_CTRL_DOWN) { pm_runtime_get_noresume(ctrl->ctrl.dev); ctrl->state = QCOM_SLIM_NGD_CTRL_DOWN; qcom_slim_ngd_down(ctrl); qcom_slim_ngd_exit_dma(ctrl); } - mutex_unlock(&ctrl->tx_lock); break; case QCOM_SSR_AFTER_POWERUP: case SERVREG_SERVICE_STATE_UP: