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Tue, 31 Mar 2026 20:22:54 -0700 (PDT) Received: from [192.168.86.59] ([104.57.184.186]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7da0a336d73sm9589357a34.5.2026.03.31.20.22.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Mar 2026 20:22:54 -0700 (PDT) From: Bjorn Andersson Date: Tue, 31 Mar 2026 22:22:49 -0500 Subject: [PATCH v2 7/7] slimbus: qcom-ngd-ctrl: Avoid ABBA on tx_lock/ctrl->lock 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="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260331-slim-ngd-dev-v2-7-9441e9c8420e@oss.qualcomm.com> References: <20260331-slim-ngd-dev-v2-0-9441e9c8420e@oss.qualcomm.com> In-Reply-To: <20260331-slim-ngd-dev-v2-0-9441e9c8420e@oss.qualcomm.com> To: Srinivas Kandagatla , Greg Kroah-Hartman , Vinod Koul , Krzysztof Kozlowski Cc: linux-arm-msm@vger.kernel.org, linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, Bjorn Andersson , stable@vger.kernel.org X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; 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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 (drive= rs/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 suppor= t") Cc: stable@vger.kernel.org Signed-off-by: Bjorn Andersson --- drivers/slimbus/qcom-ngd-ctrl.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/slimbus/qcom-ngd-ctrl.c b/drivers/slimbus/qcom-ngd-ctr= l.c index afd2171d3be2c4c19994e9ebedc63dedfba899e0..2ff4374a1e0ce5d3d8f9b074f19= fe77daeb79dae 100644 --- 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(struct qcom= _slim_ngd_ctrl *ctrl, 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 !=3D QCOM_SLIM_NGD_CTRL_DOWN) { pm_runtime_get_noresume(ctrl->ctrl.dev); ctrl->state =3D 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: --=20 2.51.0