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SubjectRe: [PATCH v10 54/55] Input: atmel_mxt_ts: Implement synchronization during various operation
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Date
31.03.2020 13:50, Jiada Wang пишет:
> From: Sanjeev Chugh <sanjeev_chugh@mentor.com>
>
> There could be scope of race conditions when sysfs is being handled
> and at the same time, device removal is occurring. For example,
> we don't want the device removal to begin if the Atmel device
> cfg update is going on or firmware update is going on. In such
> cases, wait for device update to be completed before the removal
> continues.
>
> Thread Thread 2:
> ========================= =========================
> mxt_update_fw_store() mxt_remove()
> mutex_lock(&data->lock) ...
> mxt_initialize() //Tries to acquire lock
> request_firmware_nowait() mutex_lock(&data->lock)
> ... ==>waits for lock()
> ... .
> ... .
> mutex_unlock(&data->lock) .
> //Gets lock and proceeds
> mxt_free_input_device();
> ...
> mutex_unlock(&data->lock)
> //Frees atmel driver data
> kfree(data)
>
> If the request_firmware_nowait() completes after the driver removal,
> and callback is triggered. But kernel crashes since the module is
> already removed.
>
> This commit adds state machine to serialize such scenarios.

Won't it be easier to bump driver's module use-count by __module_get()
while firmware is updating? Or remove sysfs during of mxt_remove()?

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