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SubjectRe: [PATCH v2 1/3] venus: core: handle race condititon for core ops
On 2020-09-11 15:40, Stanimir Varbanov wrote:
> On 9/10/20 3:44 PM, Mansur Alisha Shaik wrote:
>> For core ops we are having only write protect but there
>> is no read protect, because of this in multthreading
>> and concurrency, one CPU core is reading without wait
>> which is causing the NULL pointer dereferece crash.
>>
>> one such scenario is as show below, where in one CPU
>> core, core->ops becoming NULL and in another CPU core
>> calling core->ops->session_init().
>>
>> CPU: core-7:
>> Call trace:
>> hfi_session_init+0x180/0x1dc [venus_core]
>> vdec_queue_setup+0x9c/0x364 [venus_dec]
>> vb2_core_reqbufs+0x1e4/0x368 [videobuf2_common]
>> vb2_reqbufs+0x4c/0x64 [videobuf2_v4l2]
>> v4l2_m2m_reqbufs+0x50/0x84 [v4l2_mem2mem]
>> v4l2_m2m_ioctl_reqbufs+0x2c/0x38 [v4l2_mem2mem]
>> v4l_reqbufs+0x4c/0x5c
>> __video_do_ioctl+0x2b0/0x39c
>>
>> CPU: core-0:
>> Call trace:
>> venus_shutdown+0x98/0xfc [venus_core]
>> venus_sys_error_handler+0x64/0x148 [venus_core]
>> process_one_work+0x210/0x3d0
>> worker_thread+0x248/0x3f4
>> kthread+0x11c/0x12c
>>
>> Signed-off-by: Mansur Alisha Shaik <mansur@codeaurora.org>
>> Acked-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
>> ---
>> Changes in V2:
>> - Addressed review comments by stan by validating on top
>> - of
>> https://lore.kernel.org/patchwork/project/lkml/list/?series=455962
>>
>> drivers/media/platform/qcom/venus/hfi.c | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/platform/qcom/venus/hfi.c
>> b/drivers/media/platform/qcom/venus/hfi.c
>> index a59022a..3137071 100644
>> --- a/drivers/media/platform/qcom/venus/hfi.c
>> +++ b/drivers/media/platform/qcom/venus/hfi.c
>> @@ -195,7 +195,7 @@ EXPORT_SYMBOL_GPL(hfi_session_create);
>> int hfi_session_init(struct venus_inst *inst, u32 pixfmt)
>> {
>> struct venus_core *core = inst->core;
>> - const struct hfi_ops *ops = core->ops;
>> + const struct hfi_ops *ops;
>> int ret;
>>
>
> If we are in system error recovery the session_init cannot pass
> successfully, so we exit early in the function.
>
> I'd suggest to make it:
>
> /* If core shutdown is in progress or we are in system error
> recovery,
> return an error */
> mutex_lock(&core->lock);
> if (!core->ops || core->sys_error) {
> mutex_unclock(&core->lock);
> return -EIO;
> }
> mutex_unclock(&core->lock);
>
Tried above suggestion and ran the failed scenario, I didn't see any
issue.
Posted new version
https://lore.kernel.org/patchwork/project/lkml/list/?series=463091
>> if (inst->state != INST_UNINIT)
>> @@ -204,10 +204,13 @@ int hfi_session_init(struct venus_inst *inst,
>> u32 pixfmt)
>> inst->hfi_codec = to_codec_type(pixfmt);
>> reinit_completion(&inst->done);
>>
>> + mutex_lock(&core->lock);
>> + ops = core->ops;
>> ret = ops->session_init(inst, inst->session_type, inst->hfi_codec);
>> if (ret)
>> return ret;
>>
>> + mutex_unlock(&core->lock);
>> ret = wait_session_msg(inst);
>> if (ret)
>> return ret;
>>

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