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([2001:b07:2ec:601d:4b26:1672:75c7:805a]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c4cebf3cadbsm90903766b.50.2026.11.03.06.24.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Nov 2026 06:24:55 -0800 (PST) Message-ID: Date: Tue, 3 Nov 2026 15:24:53 +0100 X-Mailing-List: linux-arm-msm@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 v2 3/4] drm/msm/debugfs: Use cleanup.h for gpu state dump To: rob.clark@oss.qualcomm.com, Konrad Dybcio Cc: dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, Dmitry Baryshkov , Abhinav Kumar , Jessica Zhang , Sean Paul , Marijn Suijten , David Airlie , Simona Vetter , open list References: <20261102190010.720443-1-robin.clark@oss.qualcomm.com> <20261102190010.720443-4-robin.clark@oss.qualcomm.com> Content-Language: en-US From: Anna Maniscalco In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 11/3/26 2:58 PM, Rob Clark wrote: > On Tue, Nov 3, 2026 at 3:28 AM Konrad Dybcio > wrote: >> On 11/2/26 8:00 PM, Rob Clark wrote: >>> We need to move the gpu lock around a bit for the next patch. Use >>> scoped_guard/etc so we don't have to make the error path handling more >>> complicated. >>> >>> Signed-off-by: Rob Clark >>> --- >>> drivers/gpu/drm/msm/msm_debugfs.c | 31 ++++++++++++------------------- >>> 1 file changed, 12 insertions(+), 19 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/msm/msm_debugfs.c b/drivers/gpu/drm/msm/msm_debugfs.c >>> index f12701e286ec..aa59b28a3392 100644 >>> --- a/drivers/gpu/drm/msm/msm_debugfs.c >>> +++ b/drivers/gpu/drm/msm/msm_debugfs.c >>> @@ -70,43 +70,36 @@ static int msm_gpu_open(struct inode *inode, struct file *file) >>> struct drm_device *dev = inode->i_private; >>> struct msm_drm_private *priv = dev->dev_private; >>> struct msm_gpu *gpu = priv->gpu; >>> - struct msm_gpu_show_priv *show_priv; >>> int ret; >>> >>> if (!gpu || !gpu->funcs->gpu_state_get) >>> return -ENODEV; >>> >>> - show_priv = kmalloc_obj(*show_priv); >>> + struct msm_gpu_show_priv *show_priv __free(kfree) >>> + = kmalloc_obj(*show_priv); >>> if (!show_priv) >>> return -ENOMEM; >>> >>> - ret = mutex_lock_interruptible(&gpu->lock); >>> - if (ret) >>> - goto free_priv; >>> - >>> - pm_runtime_get_sync(&gpu->pdev->dev); >>> - msm_gpu_hw_init(gpu); >>> - show_priv->state = gpu->funcs->gpu_state_get(gpu); >>> - pm_runtime_put_sync(&gpu->pdev->dev); >>> - >>> - mutex_unlock(&gpu->lock); >>> + scoped_guard (pm_runtime_active, &gpu->pdev->dev) { >>> + scoped_cond_guard (mutex_intr, return -EINTR, &gpu->lock) { >>> + msm_gpu_hw_init(gpu); >>> + show_priv->state = gpu->funcs->gpu_state_get(gpu); >>> + } >> My clanker tells me we can't grab the PM reference before a mutex, >> as the recovery mechanism depends on the rpm count being appropriate >> to let it drop it (and kill gx this way) > Yeah, but we also can't do it in the other order, or more specifically > disabling ifpc needs to come before gpu lock or it can deadlock with > recovery.. but ifpc disable needs to be after runpm get. > > Re-working that ordering was the whole of introducing cleanup.h, to > avoid the error path with mutex_lock_interruptible() after taking > runpm > > I guess if you are hammering on debugfs while crashing the gpu, maybe > the first recovery fails, and then a subsequent one eventually > succeeds. I guess it leads to a sort of deadlock scenario because the recovery path waits for power to collapse, though it timeouts after one second. After that hangcheck will have to trigger again so I guess the delay introduced would be significant. I really wish there was some better way of doing recovery that didn't rely on the counbter having a known value. > > BR, > -R Best regards, -- Anna Maniscalco