Re: Serial: UART_BUG_TXEN race conditions

[Ingo van Lil <inguin@gmx.de>]

Russell King <rmk+lkml@arm.linux.org.uk> schrieb:

> > 1. What if the IIR actually equals UART_IIR_THRI at that point? The
> >    read access will clear the interrupt condition and the workaround
> >    will effect the actual opposite of its intention: Neither
> >    serial8250_start_tx() nor the interrupt handler will start
> >    transmitting characters for the ring buffer.
>
> Gah, looks like you're right - reading the IIR will clear the transmit
> pending interrupt, so we should probably just load the transmitter up
> with characters anyway if the TEMT bit is set.

How about doing that on any controller, not just the buggy ones? It 
shouldn't cause any problems even on well-behaved UARTs, or could it?

> This function is run under the port spinlock, so the interrupt handler
> will be held off until it completes.

OK, great. Forget about my second concern, then.

Cheers,
Ingo


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