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Date: Tue, 23 Nov 2021 14:57:26 -0800
From: Peter Collingbourne <pcc@...gle.com>
To: Tadeusz Struk <tadeusz.struk@...aro.org>
Cc: Stanimir Varbanov <stanimir.varbanov@...aro.org>,
Andy Gross <agross@...nel.org>,
Bjorn Andersson <bjorn.andersson@...aro.org>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Lee Jones <lee.jones@...aro.org>,
Amit Pundir <amit.pundir@...aro.org>,
John Stultz <john.stultz@...aro.org>,
linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] media: venus: Synchronize probe() between venus_core
and enc/dec
On Fri, Oct 29, 2021 at 02:48:33PM -0700, Tadeusz Struk wrote:
> Venus video encode/decode hardware driver consists of three modules.
> The parent module venus-core, and two sub modules venus-enc and venus-dec.
> The venus-core module allocates a common structure that is used by the
> enc/dec modules, loads the firmware, and performs some common hardware
> initialization. Since the three modules are loaded one after the other,
> and their probe functions can run in parallel it is possible that
> the venc_probe and vdec_probe functions can finish before the core
> venus_probe function, which then can fail when, for example it
> fails to load the firmware. In this case the subsequent call to venc_open
> causes an Oops as it tries to dereference already uninitialized structures
> through dev->parent and the system crashes in __pm_runtime_resume() as in
> the trace below:
>
> [ 26.064835][ T485] Internal error: Oops: 96000006 [#1] PREEMPT SMP
> [ 26.270914][ T485] Hardware name: Thundercomm Dragonboard 845c (DT)
> [ 26.285019][ T485] pc : __pm_runtime_resume+0x34/0x178
> [ 26.286374][ T213] lt9611 10-003b: hdmi cable connected
> [ 26.290285][ T485] lr : venc_open+0xc0/0x278 [venus_enc]
> [ 26.290326][ T485] Call trace:
> [ 26.290328][ T485] __pm_runtime_resume+0x34/0x178
> [ 26.290330][ T485] venc_open+0xc0/0x278 [venus_enc]
> [ 26.290335][ T485] v4l2_open+0x184/0x294
> [ 26.290340][ T485] chrdev_open+0x468/0x5c8
> [ 26.290344][ T485] do_dentry_open+0x260/0x54c
> [ 26.290349][ T485] path_openat+0xbe8/0xd5c
> [ 26.290352][ T485] do_filp_open+0xb8/0x168
> [ 26.290354][ T485] do_sys_openat2+0xa4/0x1e8
> [ 26.290357][ T485] __arm64_compat_sys_openat+0x70/0x9c
> [ 26.290359][ T485] invoke_syscall+0x60/0x170
> [ 26.290363][ T485] el0_svc_common+0xb8/0xf8
> [ 26.290365][ T485] do_el0_svc_compat+0x20/0x30
> [ 26.290367][ T485] el0_svc_compat+0x24/0x84
> [ 26.290372][ T485] el0t_32_sync_handler+0x7c/0xbc
> [ 26.290374][ T485] el0t_32_sync+0x1b8/0x1bc
> [ 26.290381][ T485] ---[ end trace 04ca7c088b4c1a9c ]---
> [ 26.290383][ T485] Kernel panic - not syncing: Oops: Fatal exception
>
> This can be fixed by synchronizing the three probe functions and
> only allowing the venc_probe() and vdec_probe() to pass when venus_probe()
> returns success.
>
> Changes in v2:
> - Change locking from mutex_lock to mutex_trylock
> in venc_probe and vdec_probe to avoid potential deadlock.
>
> Signed-off-by: Tadeusz Struk <tadeusz.struk@...aro.org>
I've had this patched in, no crashes so far after several reboots.
Tested-by: Peter Collingbourne <pcc@...gle.com>
Peter
> ---
> drivers/media/platform/qcom/venus/core.c | 6 ++++++
> drivers/media/platform/qcom/venus/core.h | 2 ++
> drivers/media/platform/qcom/venus/vdec.c | 24 +++++++++++++++++++++---
> drivers/media/platform/qcom/venus/venc.c | 24 +++++++++++++++++++++---
> 4 files changed, 50 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
> index 91b15842c555..18f3e3a9823f 100644
> --- a/drivers/media/platform/qcom/venus/core.c
> +++ b/drivers/media/platform/qcom/venus/core.c
> @@ -317,6 +317,7 @@ static int venus_probe(struct platform_device *pdev)
>
> INIT_LIST_HEAD(&core->instances);
> mutex_init(&core->lock);
> + mutex_init(&core->sync_lock);
> INIT_DELAYED_WORK(&core->work, venus_sys_error_handler);
>
> ret = devm_request_threaded_irq(dev, core->irq, hfi_isr, hfi_isr_thread,
> @@ -331,6 +332,8 @@ static int venus_probe(struct platform_device *pdev)
>
> venus_assign_register_offsets(core);
>
> + mutex_lock(&core->sync_lock);
> +
> ret = v4l2_device_register(dev, &core->v4l2_dev);
> if (ret)
> goto err_core_deinit;
> @@ -377,6 +380,7 @@ static int venus_probe(struct platform_device *pdev)
> goto err_dev_unregister;
> }
>
> + mutex_unlock(&core->sync_lock);
> venus_dbgfs_init(core);
>
> return 0;
> @@ -392,6 +396,7 @@ static int venus_probe(struct platform_device *pdev)
> hfi_destroy(core);
> err_core_deinit:
> hfi_core_deinit(core, false);
> + mutex_unlock(&core->sync_lock);
> err_core_put:
> if (core->pm_ops->core_put)
> core->pm_ops->core_put(core);
> @@ -428,6 +433,7 @@ static int venus_remove(struct platform_device *pdev)
>
> mutex_destroy(&core->pm_lock);
> mutex_destroy(&core->lock);
> + mutex_destroy(&core->sync_lock);
> venus_dbgfs_deinit(core);
>
> return ret;
> diff --git a/drivers/media/platform/qcom/venus/core.h b/drivers/media/platform/qcom/venus/core.h
> index 5ec851115eca..3f80dc26febb 100644
> --- a/drivers/media/platform/qcom/venus/core.h
> +++ b/drivers/media/platform/qcom/venus/core.h
> @@ -119,6 +119,7 @@ struct venus_format {
> * @use_tz: a flag that suggests presence of trustzone
> * @fw: structure of firmware parameters
> * @lock: a lock for this strucure
> + * @sync_lock a lock for probe sync between venus_core and venus_enc/dec
> * @instances: a list_head of all instances
> * @insts_count: num of instances
> * @state: the state of the venus core
> @@ -176,6 +177,7 @@ struct venus_core {
> size_t mem_size;
> } fw;
> struct mutex lock;
> + struct mutex sync_lock;
> struct list_head instances;
> atomic_t insts_count;
> unsigned int state;
> diff --git a/drivers/media/platform/qcom/venus/vdec.c b/drivers/media/platform/qcom/venus/vdec.c
> index 198e47eb63f4..959e43bb6c00 100644
> --- a/drivers/media/platform/qcom/venus/vdec.c
> +++ b/drivers/media/platform/qcom/venus/vdec.c
> @@ -1659,17 +1659,32 @@ static int vdec_probe(struct platform_device *pdev)
> if (!core)
> return -EPROBE_DEFER;
>
> + /* Sync and wait on the venus core to initialize first.
> + * If we manage to acquire the sync_lock here it means
> + * that the venus_probe() finished running */
> + ret = mutex_trylock(&core->sync_lock);
> + if (!ret) {
> + return -EPROBE_DEFER;
> + } else {
> + if (core->state != CORE_INIT) {
> + ret = -ENODEV;
> + goto err_core_unlock;
> + }
> + }
> +
> platform_set_drvdata(pdev, core);
>
> if (core->pm_ops->vdec_get) {
> ret = core->pm_ops->vdec_get(dev);
> if (ret)
> - return ret;
> + goto err_core_unlock;
> }
>
> vdev = video_device_alloc();
> - if (!vdev)
> - return -ENOMEM;
> + if (!vdev) {
> + ret = -ENOMEM;
> + goto err_core_unlock;
> + }
>
> strscpy(vdev->name, "qcom-venus-decoder", sizeof(vdev->name));
> vdev->release = video_device_release;
> @@ -1690,11 +1705,14 @@ static int vdec_probe(struct platform_device *pdev)
> pm_runtime_set_autosuspend_delay(dev, 2000);
> pm_runtime_use_autosuspend(dev);
> pm_runtime_enable(dev);
> + mutex_unlock(&core->sync_lock);
>
> return 0;
>
> err_vdev_release:
> video_device_release(vdev);
> +err_core_unlock:
> + mutex_unlock(&core->sync_lock);
> return ret;
> }
>
> diff --git a/drivers/media/platform/qcom/venus/venc.c b/drivers/media/platform/qcom/venus/venc.c
> index bc1c42dd53c0..11ec7bff5e3f 100644
> --- a/drivers/media/platform/qcom/venus/venc.c
> +++ b/drivers/media/platform/qcom/venus/venc.c
> @@ -1338,17 +1338,32 @@ static int venc_probe(struct platform_device *pdev)
> if (!core)
> return -EPROBE_DEFER;
>
> + /* Sync and wait on the venus core to initialize first.
> + * If we manage to acquire the sync_lock here it means
> + * that the venus_probe() finished running */
> + ret = mutex_trylock(&core->sync_lock);
> + if (!ret) {
> + return -EPROBE_DEFER;
> + } else {
> + if (core->state != CORE_INIT) {
> + ret = -ENODEV;
> + goto err_core_unlock;
> + }
> + }
> +
> platform_set_drvdata(pdev, core);
>
> if (core->pm_ops->venc_get) {
> ret = core->pm_ops->venc_get(dev);
> if (ret)
> - return ret;
> + goto err_core_unlock;
> }
>
> vdev = video_device_alloc();
> - if (!vdev)
> - return -ENOMEM;
> + if (!vdev) {
> + ret = -ENOMEM;
> + goto err_core_unlock;
> + }
>
> strscpy(vdev->name, "qcom-venus-encoder", sizeof(vdev->name));
> vdev->release = video_device_release;
> @@ -1367,11 +1382,14 @@ static int venc_probe(struct platform_device *pdev)
>
> video_set_drvdata(vdev, core);
> pm_runtime_enable(dev);
> + mutex_unlock(&core->sync_lock);
>
> return 0;
>
> err_vdev_release:
> video_device_release(vdev);
> +err_core_unlock:
> + mutex_unlock(&core->sync_lock);
> return ret;
> }
>
> --
> 2.31.1
>
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