[Barrelfish-users] No serial input

Simon Gerber simu at vis.ethz.ch
Tue Nov 8 13:06:21 CET 2011


 From what I can tell, if terminal_want_stdin needs to look up and bind 
to the serial service, the code after the lookup runs before the bind_cb 
completes and thus the check for state->serial != NULL before 
associating stdin fails and terminal_want_stdin returns with SYS_ERR_OK 
without having actually grabbed stdin.

I assume this should be fixed by busy-waiting on the completion of 
serial_bind_cb? Or is there a better way of doing this?


-- Simon Gerber

On Sun, 6 Nov 2011 17:26:47 +0000, Baumann  Andrew wrote:
> Hi,
> This sounds like a startup race. I can't tell you the solution, but I
> can give you clues where to look: lib/barrelfish/terminal.c
> terminal_init() does a  nonblocking lookup for the serial driver, and
> if it is already registered, it connects to it. Otherwise if it isn't
> already present, fish's main() will start without a binding to the
> serial driver, but the call to terminal_want_stdin() should cause the
> binding to be established (this time in a blocking fashion), assuming
> you didn't pass "keyboard" as one of the command-line parameters to
> fish. I would stick some debug into terminal.c and try to understand
> what is happening when you block.
> Hope this helps,
> Andrew
>> -----Original Message-----
>> From: Mark Nevill [mailto:nevillm at ethz.ch]
>> Sent: Thursday, 3 November 2011 16:01
>> To: barrelfish-users at lists.inf.ethz.ch
>> Subject: [Barrelfish-users] No serial input
>> Hi everyone!
>> When booting Barrelfish repeatedly in qemu, rarely the two lines 
>> below
>> appear:
>> chips: client waiting for serial
>> chips: notifying client about serial
>> If these lines appear, fish does not receive serial input.
>> This particularly affects our pending merge of our AHCI driver
>> project, as we get these messages far more often (this is probably 
>> due
>> to the AHCI driver delaying the initialisation of the serial 
>> driver).
>> Has anybody else encountered this issue?
>> Regards,
>> -- Mark & Simon
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