HID: uhid: allow poll()'ing on uhid devices
As long as the internal buffer is not empty, we return POLLIN to user-space. uhid->head and uhid->tail are no atomics so the comparison may return inexact results. However, this doesn't matter here as user-space would need to poll() in two threads simultaneously to trigger this. And in this case it doesn't matter if a cached result is returned or the exact new result as user-space does not know which thread returns first from poll() and the following read(). So it is safe to compare the values without locking. Signed-off-by:David Herrmann <dh.herrmann@googlemail.com> Signed-off-by:
Jiri Kosina <jkosina@suse.cz>
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