RE: PROBLEM: kernel oops with g_serial USB gadget on 2.6.30

Hello,

On Tuesday, June 23, 2009 11:21 AM, Alan Cox wrote:

that g_serial driver interacts with tty layer in that packet_done
callback,
so this is the source of the problems. I noticed that some other UDC
drivers also does all its job from an interrupt, so they also might
be
affected. How this bug should be properly resolved?

Either by not setting ->low_latency or by running the data paths from a
non IRQ context.

Basically: don't set tty->low_latency if you are handling the
processing
from the IRQ path. The only case low_latency is useful is handling data
from a non-IRQ path where you have latency concerns for tx/rx
switching.

I know that, but I wonder how this should be handled in g_serial gadget
driver, which might be working on top of both types of low level
drivers (doing callback from irq or tasklet).

Are there any drawbacks of disabling low_latency mode if callbacks are
done from tasklet not from interrupt? If no then the low latency mode
should be disabled in g_serial driver.

Best regards
--
Marek Szyprowski
Samsung Poland R&D Center


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