Re: [PATCH 0/2] fixes for empty tx buffer breakage

[Greg KH]

On Thu, Jul 10, 2014 at 04:12:05PM -0700, David Miller wrote:
> From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Date: Thu, 10 Jul 2014 16:14:32 -0700
> 
> > On Sun, Jul 06, 2014 at 11:29:51AM -0400, Peter Hurley wrote:
> >> Cc: Seth Bollinger <sethb@xxxxxxxx>
> >> Cc: Aaro Koskinen <aaro.koskinen@xxxxxx>
> >> Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
> >> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> >> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> >> 
> >> Greg,
> >> 
> >> I completed the audit of serial drivers after reports that
> >> several Sun serial drivers were broken by
> >> commit 717f3bbab3c7628736ef738fdbf3d9a28578c26c,
> >> 'serial_core: Fix conditional start_tx on ring buffer not empty'.
> >> 
> >> I apologize for not submitting this sooner. The delay was due to
> >> an ongoing analysis of serial flow control prompted by Sam Ravnborg's
> >> question:
> >> 
> >> On 06/10/2014 03:24 PM, Sam Ravnborg wrote:
> >> > I also noticed the typical pattern is:
> >> > 
> >> >      if (uart_circ_empty(xmit) || uart_tx_stopped(port))
> >> > 
> >> > Should you use this pattern also in sunsab.c?
> >> 
> >> Unfortunately, that analysis revealed that tx flow control is
> >> largely SMP-unsafe, and it's fairly easy to corrupt the hardware
> >> state wrt. the tty flow control state.
> >> 
> >> I'm still working on the solutions to that; they're too
> >> extensive to submit for 3.16 anyway.
> > 
> > So these should go into 3.16-final?  Or 3.17?
> 
> Definitely 3.16, this regression is several releases old.

Ok, will queue it up, thanks.

gre gk-h
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