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Thu, 05 Nov 2026 00:22:37 -0800 (PST) Received: from [192.168.226.1] ([178.235.128.140]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6b57e26b0ffsm438510a12.32.2026.11.05.00.22.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Nov 2026 00:22:35 -0800 (PST) Message-ID: <2711cffc-81b0-4078-b3a4-decad4969e33@oss.qualcomm.com> Date: Thu, 5 Nov 2026 09:22:32 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6/6] backlight: qcom-wled: Avoid AB-BA deadlock in wled_module_enable() To: Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller , Kiran Gunda , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, David Heidelberg References: <20261104183935.1214630-1-lee@kernel.org> <20261104183935.1214630-7-lee@kernel.org> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <20261104183935.1214630-7-lee@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Authority-Analysis: v=2.4 cv=Vtm2kO2n c=1 sm=1 tr=0 ts=6aec3cce cx=c_pps a=7E5Bxpl4vBhpaufnMqZlrw==:117 a=PRfkaYvzSr8QmIIGAkY2Sg==:17 a=IkcTkHD0fZMA:10 a=zJRp6_cAMcgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=3WHJM1ZQz_JShphwDgj5:22 a=c92rfblmAAAA:8 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=cyDCuRFuYf_2H7WJZrMA:9 a=QEXdDO2ut3YA:10 a=pJ04lnu7RYOZP9TFuWaZ:22 a=GvGzcOZaWPEFPQC_NcjD:22 X-Proofpoint-Spam-Info: AW1haW4tMjYxMTA1MDAzMyBTYWx0ZWRfX4InbrFJELR80 IuuLKWNrFn3T1M/d/pAwdNAZQg35eGW3bc4zrgMdSt2in6Y9OXYTWeAtbdyrA6ze2a4C6VaqntR 5y/Iu4ZbYKBqW/ED0Umb5j7J+EAakdI= X-Proofpoint-ORIG-GUID: LKfZXK-TgoxIU5Ek3IOpdmv5OzMw671J X-Proofpoint-GUID: LKfZXK-TgoxIU5Ek3IOpdmv5OzMw671J X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTA1MDAzMyBTYWx0ZWRfX948UnPmWEd9O Rz1zSobzs+HgQ5PCL4AY33qhNi3vRPujo7pwDH8+MqUS/pGRfBNaapv8+AJ/R7LpFOIziIFNa/e Z479gFJb2pkU9MIvaFWZ8aUylk4DFx+G7iajA17XMk0y02McPyMjrc7AbGyeHte7OS1i9VbcM7l 6hPEgR7QV6756TftcYHH3HwyK0Sh4AQ1l2H/ucu7k8pGjZNJuQciMgBAtpJCpDVgz80sCgpWm7y ja9g+jwEfBQrptd87xoic8bo6p2Z2zt1ls6JLW1NVUjMRWZ4wl0CrjncyfUnX1263Srraam0mk8 v+mGmhOj6N33x2eDlRB++UKfV3lV2pBzDEGTlRuHunHUdFkHlHh0rgu5x8/M5SCeRN0+20Tk+sB c+CRlKTVl+vn10NLlyMlwsn8VXZEAo96NU1dY/00QnyFUSDc68+7hQ4aFvkZmwVHkdslKlDMjHR dXG55EOu8Avj+YYrShQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-05_02,2026-11-04_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 impostorscore=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 lowpriorityscore=0 priorityscore=1501 clxscore=1015 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610300000 definitions=main-2611050033 On 11/4/26 7:39 PM, Lee Jones wrote: > When disabling the WLED module (for example from wled_update_status() or > wled_short_irq_handler()), the caller holds wled->lock and invokes > wled_module_enable(wled, false), which calls disable_irq(wled->ovp_irq) > and blocks waiting for any executing OVP threaded interrupt handler to > complete. > > If wled_ovp_irq_handler() is concurrently executing, it attempts to > acquire wled->lock before running wled_auto_string_detection(), > resulting in an AB-BA deadlock between wled->lock and IRQ completion. > > Use disable_irq_nosync() instead of disable_irq() in > wled_module_enable() so that the OVP interrupt is masked without > synchronously waiting for the threaded handler while holding wled->lock. > Because wled_ovp_irq_handler() may already be waiting on wled->lock when > the module is disabled, verify under wled->lock that the module is still > enabled and not disabled by a short before running > wled_auto_string_detection(). > > Fixes: 8663c188beea ("backlight: qcom-wled: Add auto string detection logic") > Closes: https://sashiko.dev/#/bug/linux-3afa151c-7b8f-432c-8f85-8c43a83b964a > Cc: stable@vger.kernel.org > Signed-off-by: Lee Jones > --- Acked-by: Konrad Dybcio Konrad