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From: Ian Abbott on 6 May 2010 08:50
Hi Tobias,

On 06/05/10 13:03, Tobias Klauser wrote:
> I also noticed, that altera_uart_break_ctl takes the lock which might be
> not necessary as the caller in serial_core.c already takes port->mutex
> which should be enough. Or am I wrong?

It's not enough. The spin lock is needed to protect modification of
pp->imr and writing this modified value to the control register. Not
all paths that modify pp->imr and the control register grab port->mutex
beforehand (for example, the interrupt routine doesn't and can't).

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