Re: [uclinux-dist-devel] [PATCH] serial: bfin_5xx: split uart RX lock from uart port lock to avoid deadlock

[Mike Frysinger <vapier@gentoo.org>]

On Tue, Jan 11, 2011 at 00:16, Mike Frysinger wrote:
> From: Sonic Zhang <sonic.zhang@analog.com>
>
> The RX lock is used to protect the RX buffer from concurrent access in DMA
> mode between the timer and RX interrupt routines.  It is independent from
> the uart lock which is used to protect the TX buffer.  It is possible for
> a uart TX transfer to be started up from the RX interrupt handler if low
> latency is enabled.  So we need to split the locks to avoid deadlocking in
> this situation.
>
> In PIO mode, the RX lock is not necessary because the handle_simple_irq
> and handle_level_irq functions ensure driver interrupt handlers are called
> once on one core.
>
> And now that the RX path has its own lock, the TX interrupt has nothing to
> do with the RX path, so disabling it at the same time.

ping ...
-mike
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