Re: stty: problem if IXON enabled and DC3 char was received

[Pádraig Brady]

On 04/01/16 10:27, Pádraig Brady wrote:
> On 04/01/16 08:06, Tomas Krcka wrote:
>> Hi,
>>   I had a problem with setting baudrate of serial line by stty command.
>> I tried to change the baudrate, but the stty went to frozen state.
>> I found out that problem is that kernel has IXON enabled as default
>> and before change of speed the line received DC3 char. It's illegal
>> character in this situation, it happens once per 100 starts of the
>> system.
>>
>> Example situation:
>>    IXON is enabled in kernel by default and a serial line received DC3
>> char and then you can not disable IXON. There is waiting for empty
>> buffer in kernel but sending is stopped because of DC3 char.
>>
>> If TCSADRAIN is changed to TCSANOW then it's correct.
>>
>> Do you have any opinion about the situation ? Is it possible to change
>> TCSADRAIN to TCSANOW or create a new parameter of stty to change the
>> serial line settings immediately ?
> 
> Interesting. I see that Red Hat systems for the last 6 years
> have unconditionally used TCSANOW rather than TCSADRAIN due to:
> https://bugzilla.redhat.com/504798
> 
> I see a similar 13 year old request to debian:
> https://bugs.debian.org/210475
> 
> I see that FreeBSD uses TCSANOW (well the equivalent 0 value).
> 
> Now it's tempting to use TCSANOW unconditionally
> though it does seem safer to drain pending output before changing settings,
> so an option like you suggest seems appropriate.

-I, --immediate option added in the attached

stty-immediate.patch
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