On 09/08/2016 10:15 AM, Gregor Boirie wrote:
> Hi Lars,
>
> On 09/07/2016 08:13 PM, Lars-Peter Clausen wrote:
>> On 09/07/2016 07:26 PM, Gregor Boirie wrote:
>>> Using iio_device_unregister() on a device currently in use may stall
>>> userspace process polling for data availability (poll syscall).
>>>
>>> If device has vanished before running the iio_buffer_fileops poll hook, the
>>> latter will return empty poll event mask. Process will be stalled waiting
>>> for events that will never come (if no timeout specified).
>>>
>>> This patch ensures iio_buffer_poll() returns POLLERR if device has just
>>> been unregistered in order to properly notify userspace process something
>>> wrong happened (such as removable device unplugged).
>>>
>>> Fixes: 1bdc029390 ("iio: industrialio-buffer: Fix iio_buffer_poll return
>>> value")
>>> Signed-off-by: Gregor Boirie <gregor.boirie@xxxxxxxxxx>
>> Hi,
>>
>> Thanks for the patch. I agree with the solution, I don't quite agree with
>> the description. In my opinion the current behavior is not necessarily a
>> bug. Obviously there won't be a wakeup when the device has been removed
>> since no new data will be generated. But there are other scenarios where
>> this can happen as well (e.g. broken hardware). An application should be
>> prepared to handle this and if it is interactive for example allow the user
>> to interrupt the capture process.
> Ok. What do you want me to do then ? Remove the "Fixes" tag ? Reword
> something in the commit log ?
> I'll merge the 2 patches as recommended by Jonathan anyway.
I'd drop the Fixes tag and maybe change the subject to "Let poll report an
error for unregistered devices"
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