Serial console unusable with poky-image-sdk

Serial console unusable with poky-image-sdk

[Wolfgang Denk]

Hi,

it seems that for some time (probably back to laverne-4.0) the serial
console port is basicly unusable in the poky-image-sdk file system.
I tried this in several PPC and ARM configurations, and the behaviours
is pretty much the same: login works fine, but at the shell prompt
only one out of N input characters (N usually between 2 and 10) gets
through to the shell.

I found that dbus-launch (running as "dbus-launch --sh-syntax
--exit-with-session") is also reading from /dev/console and "eating"
the missing characters.

As soon as I stop the Xserver ("sh /etc/init.d/xserver-nodm stop")
the serial console starts wroking fine (because dbus-launch is not
running any more).

Is there a way to stop dbus-launch from concurring with a login shell
on the serial console port?

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
Do not follow where the path may lead....go instead where there is no
path and leave a trail.

Re: Serial console unusable with poky-image-sdk

[Wolfgang Denk]

Hi,

in message <20110127111132.C69A3B335@gemini.denx.de> I wrote:
> 
> it seems that for some time (probably back to laverne-4.0) the serial
> console port is basicly unusable in the poky-image-sdk file system.
> I tried this in several PPC and ARM configurations, and the behaviours
> is pretty much the same: login works fine, but at the shell prompt
> only one out of N input characters (N usually between 2 and 10) gets
> through to the shell.
...
> Is there a way to stop dbus-launch from concurring with a login shell
> on the serial console port?

This patch appears to be working fine for me:

>From: Wolfgang Denk <wd@denx.de>
>Subject: Stop dbus-launch from interfering with a serial console

Signed-off-by: Wolfgang Denk <wd@denx.de>
---

diff --git a/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession b/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
index a87447a..0b73127 100644
--- a/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
+++ b/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
@@ -2,7 +2,7 @@
 
 if [ -x /usr/bin/dbus-launch ]; then
     # As this is the X session script, always start a new DBus session.
-    eval `dbus-launch --sh-syntax --exit-with-session`
+    eval `dbus-launch --sh-syntax --exit-with-session </dev/null`
     echo "D-BUS per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
 fi
 

---

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
The first thing we do is kill all the lawyers.
(Shakespeare. II Henry VI, Act IV, scene ii)

Re: Serial console unusable with poky-image-sdk

[Darren Hart]

On 01/27/2011 03:42 AM, Wolfgang Denk wrote:
> Hi,
>
> in message<20110127111132.C69A3B335@gemini.denx.de>  I wrote:
>>
>> it seems that for some time (probably back to laverne-4.0) the serial
>> console port is basicly unusable in the poky-image-sdk file system.
>> I tried this in several PPC and ARM configurations, and the behaviours
>> is pretty much the same: login works fine, but at the shell prompt
>> only one out of N input characters (N usually between 2 and 10) gets
>> through to the shell.
> ...
>> Is there a way to stop dbus-launch from concurring with a login shell
>> on the serial console port?
>
> This patch appears to be working fine for me:
>
>> From: Wolfgang Denk<wd@denx.de>
>> Subject: Stop dbus-launch from interfering with a serial console
>
> Signed-off-by: Wolfgang Denk<wd@denx.de>
> ---
>
> diff --git a/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession b/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
> index a87447a..0b73127 100644
> --- a/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
> +++ b/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
> @@ -2,7 +2,7 @@
>
>   if [ -x /usr/bin/dbus-launch ]; then
>       # As this is the X session script, always start a new DBus session.
> -    eval `dbus-launch --sh-syntax --exit-with-session`
> +    eval `dbus-launch --sh-syntax --exit-with-session</dev/null`
>       echo "D-BUS per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
>   fi
>

you can also append "console=tty" to the kernel command line and the 
serial console should work. I've run into this on a couple platforms as 
well and addressed it this way. This isn't just an X11 issue as I 
usually boot -minimal images.

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel

Re: Serial console unusable with poky-image-sdk

[Wolfgang Denk]

Dear Darren Hart,

In message <4D41F2D6.4040406@linux.intel.com> you wrote:
>
> >> Is there a way to stop dbus-launch from concurring with a login shell
> >> on the serial console port?
> >
> > This patch appears to be working fine for me:
> >
> >> From: Wolfgang Denk<wd@denx.de>
> >> Subject: Stop dbus-launch from interfering with a serial console
> >
> > Signed-off-by: Wolfgang Denk<wd@denx.de>
> > ---
> >
> > diff --git a/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession b/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
> > index a87447a..0b73127 100644
> > --- a/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
> > +++ b/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
> > @@ -2,7 +2,7 @@
> >
> >   if [ -x /usr/bin/dbus-launch ]; then
> >       # As this is the X session script, always start a new DBus session.
> > -    eval `dbus-launch --sh-syntax --exit-with-session`
> > +    eval `dbus-launch --sh-syntax --exit-with-session</dev/null`
> >       echo "D-BUS per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
> >   fi
> >
> 
> you can also append "console=tty" to the kernel command line and the 
> serial console should work. I've run into this on a couple platforms as 
> well and addressed it this way. This isn't just an X11 issue as I 
> usually boot -minimal images.

I think you misunderstand.  It is not that the serial console port is
not working at all, or that there are any wrong assignments to the
Linux console device.

The problem is that after logging in both the shell and the
dbus-launch processes will read from the same device, and it is pur
chance which of these provesses will read which input character.

The problem is that dbus-launch should not read from the console
terminal at all, and this is what above patch enforces.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
"Engineering without management is art."               - Jeff Johnson

Re: Serial console unusable with poky-image-sdk

[Darren Hart]

On 01/27/2011 11:05 PM, Wolfgang Denk wrote:
> Dear Darren Hart,
>
> In message<4D41F2D6.4040406@linux.intel.com>  you wrote:
>>
>>>> Is there a way to stop dbus-launch from concurring with a login shell
>>>> on the serial console port?
>>>
>>> This patch appears to be working fine for me:
>>>
>>>> From: Wolfgang Denk<wd@denx.de>
>>>> Subject: Stop dbus-launch from interfering with a serial console
>>>
>>> Signed-off-by: Wolfgang Denk<wd@denx.de>
>>> ---
>>>
>>> diff --git a/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession b/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
>>> index a87447a..0b73127 100644
>>> --- a/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
>>> +++ b/meta/recipes-graphics/x11-common/x11-common/etc/X11/Xsession
>>> @@ -2,7 +2,7 @@
>>>
>>>    if [ -x /usr/bin/dbus-launch ]; then
>>>        # As this is the X session script, always start a new DBus session.
>>> -    eval `dbus-launch --sh-syntax --exit-with-session`
>>> +    eval `dbus-launch --sh-syntax --exit-with-session</dev/null`
>>>        echo "D-BUS per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
>>>    fi
>>>
>>
>> you can also append "console=tty" to the kernel command line and the
>> serial console should work. I've run into this on a couple platforms as
>> well and addressed it this way. This isn't just an X11 issue as I
>> usually boot -minimal images.
>
> I think you misunderstand.  It is not that the serial console port is
> not working at all, or that there are any wrong assignments to the
> Linux console device.
>
> The problem is that after logging in both the shell and the
> dbus-launch processes will read from the same device, and it is pur
> chance which of these provesses will read which input character.
>
> The problem is that dbus-launch should not read from the console
> terminal at all, and this is what above patch enforces.

Actually, this is precisely the behavior I was seeing on other boards. 
The serial console would show all the output of the boot process and 
then present a getty. It would accept my login and my password, but as 
soon as I was logged in, things went weird. Only every Nth character I 
typed made it to the console, where N was somewhere between 2 and 30.

I believe this had something to do with the automatic consoles the 
kernel will setup based on the console= parameters. By default, the last 
console= parameter becomes /dev/console, if only serial is specified 
this seems to conflict with the getty started via inittab. If you add a 
second console directive after the first, /dev/console will point to 
that. console=/dev/tty0 works for example. Using /dev/tty however 
instructs the kernel to use an automatic console on all tty's - except 
the serial ports, which also resolves the problem for me.

What I haven't been able to explain yet is why just omitting the getty 
from the tty doesn't result in console on the serial port due to the 
kernel's automatic console thing. So clearly there are some gaps in my 
explanation here, but please try this approach and let me know what your 
results are. Based on that, we can dig a bit more and figure out how to 
best setup the console= directives on the default images.

Thanks,

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel

Re: Serial console unusable with poky-image-sdk

[Wolfgang Denk]

Dear Darren Hart,

In message <4D42F269.1080005@linux.intel.com> you wrote:
>
> The serial console would show all the output of the boot process and 
> then present a getty. It would accept my login and my password, but as 
> soon as I was logged in, things went weird. Only every Nth character I 
> typed made it to the console, where N was somewhere between 2 and 30.

Indeed. And the reason for this behaviour is that you have two
processes reading from the console, so it depends on the scheduling
which of hem receives which characters.

> I believe this had something to do with the automatic consoles the 
> kernel will setup based on the console= parameters. By default, the last 

No, it does not.  You can test it by shutting down X11 (try:
"/etc/init.d/xserver-nodm stop"); this will also terminate the
dbus-launch process, and your login shell immediately works fine.

Or try out the patch I posted.

> What I haven't been able to explain yet is why just omitting the getty 
> from the tty doesn't result in console on the serial port due to the 
> kernel's automatic console thing. So clearly there are some gaps in my 
> explanation here, but please try this approach and let me know what your 
> results are. Based on that, we can dig a bit more and figure out how to 
> best setup the console= directives on the default images.

THere is no problem with the console= settings.  It's two processes
reading from a single input stream. This can never work.  Try it ut if
you don't believe me.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
Ernest asks Frank how long he has been working for the company.
        "Ever since they threatened to fire me."

Re: Serial console unusable with poky-image-sdk

[Gary Thomas]

[-- Attachment #1: Type: text/plain, Size: 2102 bytes --]

On 01/28/2011 09:51 AM, Wolfgang Denk wrote:
> Dear Darren Hart,
>
> In message<4D42F269.1080005@linux.intel.com>  you wrote:
>>
>> The serial console would show all the output of the boot process and
>> then present a getty. It would accept my login and my password, but as
>> soon as I was logged in, things went weird. Only every Nth character I
>> typed made it to the console, where N was somewhere between 2 and 30.
>
> Indeed. And the reason for this behaviour is that you have two
> processes reading from the console, so it depends on the scheduling
> which of hem receives which characters.
>
>> I believe this had something to do with the automatic consoles the
>> kernel will setup based on the console= parameters. By default, the last
>
> No, it does not.  You can test it by shutting down X11 (try:
> "/etc/init.d/xserver-nodm stop"); this will also terminate the
> dbus-launch process, and your login shell immediately works fine.
>
> Or try out the patch I posted.
>
>> What I haven't been able to explain yet is why just omitting the getty
>> from the tty doesn't result in console on the serial port due to the
>> kernel's automatic console thing. So clearly there are some gaps in my
>> explanation here, but please try this approach and let me know what your
>> results are. Based on that, we can dig a bit more and figure out how to
>> best setup the console= directives on the default images.
>
> THere is no problem with the console= settings.  It's two processes
> reading from a single input stream. This can never work.  Try it ut if
> you don't believe me.

Wolfgang has it spot-on - both the console login and dbus are
fighting over the console device.

I've been using the equivalent of this patch for months and it
solves the problem just fine.  (Sorry I didn't report it, it
wasn't high on my list)

-- 
------------------------------------------------------------
Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
------------------------------------------------------------

[-- Attachment #2: no-stdin-for-dbus.patch --]
[-- Type: text/plain, Size: 651 bytes --]

Disconnect console from dbus - otherwise, serial console is unusable
if X session is running.

diff -ur x11-common.ORIG/etc/X11/Xsession x11-common/etc/X11/Xsession
--- x11-common.ORIG/etc/X11/Xsession	2010-08-06 06:43:51.000000000 -0600
+++ x11-common/etc/X11/Xsession	2010-07-23 12:12:00.000000000 -0600
@@ -2,7 +2,7 @@
 
 if [ -x /usr/bin/dbus-launch ]; then
     # As this is the X session script, always start a new DBus session.
-    eval `dbus-launch --sh-syntax --exit-with-session`
+    eval `dbus-launch --sh-syntax --exit-with-session </dev/null`
     echo "D-BUS per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
 fi

Re: Serial console unusable with poky-image-sdk

[Darren Hart]

On 01/28/2011 08:51 AM, Wolfgang Denk wrote:
> Dear Darren Hart,
>
> In message<4D42F269.1080005@linux.intel.com>  you wrote:
>>
>> The serial console would show all the output of the boot process and
>> then present a getty. It would accept my login and my password, but as
>> soon as I was logged in, things went weird. Only every Nth character I
>> typed made it to the console, where N was somewhere between 2 and 30.
>
> Indeed. And the reason for this behaviour is that you have two
> processes reading from the console, so it depends on the scheduling
> which of hem receives which characters.
>
>> I believe this had something to do with the automatic consoles the
>> kernel will setup based on the console= parameters. By default, the last
>
> No, it does not.  You can test it by shutting down X11 (try:
> "/etc/init.d/xserver-nodm stop"); this will also terminate the
> dbus-launch process, and your login shell immediately works fine.
>
> Or try out the patch I posted.


I'm not running X11, this is just a poky-image-minimal.


>
>> What I haven't been able to explain yet is why just omitting the getty
>> from the tty doesn't result in console on the serial port due to the
>> kernel's automatic console thing. So clearly there are some gaps in my
>> explanation here, but please try this approach and let me know what your
>> results are. Based on that, we can dig a bit more and figure out how to
>> best setup the console= directives on the default images.
>
> THere is no problem with the console= settings.  It's two processes
> reading from a single input stream. This can never work.  Try it ut if
> you don't believe me.

Agreed on the two processes thing, that's clear. I believe the console= 
settings impact which processes are started and which read from which 
console devices.

And again, I can't try your patch, because I'm not running X.

Perhaps we are seeing similar problems caused by different things.

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel

Re: Serial console unusable with poky-image-sdk

[Richard Purdie]

On Fri, 2011-01-28 at 09:16 -0800, Darren Hart wrote:
> On 01/28/2011 08:51 AM, Wolfgang Denk wrote:
> > Dear Darren Hart,
> >
> > In message<4D42F269.1080005@linux.intel.com>  you wrote:
> >>
> >> The serial console would show all the output of the boot process and
> >> then present a getty. It would accept my login and my password, but as
> >> soon as I was logged in, things went weird. Only every Nth character I
> >> typed made it to the console, where N was somewhere between 2 and 30.
> >
> > Indeed. And the reason for this behaviour is that you have two
> > processes reading from the console, so it depends on the scheduling
> > which of hem receives which characters.
> >
> >> I believe this had something to do with the automatic consoles the
> >> kernel will setup based on the console= parameters. By default, the last
> >
> > No, it does not.  You can test it by shutting down X11 (try:
> > "/etc/init.d/xserver-nodm stop"); this will also terminate the
> > dbus-launch process, and your login shell immediately works fine.
> >
> > Or try out the patch I posted.
> 
> 
> I'm not running X11, this is just a poky-image-minimal.
> 
> 
> >
> >> What I haven't been able to explain yet is why just omitting the getty
> >> from the tty doesn't result in console on the serial port due to the
> >> kernel's automatic console thing. So clearly there are some gaps in my
> >> explanation here, but please try this approach and let me know what your
> >> results are. Based on that, we can dig a bit more and figure out how to
> >> best setup the console= directives on the default images.
> >
> > THere is no problem with the console= settings.  It's two processes
> > reading from a single input stream. This can never work.  Try it ut if
> > you don't believe me.
> 
> Agreed on the two processes thing, that's clear. I believe the console= 
> settings impact which processes are started and which read from which 
> console devices.
> 
> And again, I can't try your patch, because I'm not running X.
> 
> Perhaps we are seeing similar problems caused by different things.

Regardless, I think we should take the patch since we have at least two
users seeing issues due to it.

Saul or I will ensure it gets in, I keep meaning to merge it but then
get distracted...

Cheers,

Richard

Re: Serial console unusable with poky-image-sdk

[Richard Purdie]

On Fri, 2011-01-28 at 09:56 -0700, Gary Thomas wrote:
> On 01/28/2011 09:51 AM, Wolfgang Denk wrote:
> > Dear Darren Hart,
> >
> > In message<4D42F269.1080005@linux.intel.com>  you wrote:
> >>
> >> The serial console would show all the output of the boot process and
> >> then present a getty. It would accept my login and my password, but as
> >> soon as I was logged in, things went weird. Only every Nth character I
> >> typed made it to the console, where N was somewhere between 2 and 30.
> >
> > Indeed. And the reason for this behaviour is that you have two
> > processes reading from the console, so it depends on the scheduling
> > which of hem receives which characters.
> >
> >> I believe this had something to do with the automatic consoles the
> >> kernel will setup based on the console= parameters. By default, the last
> >
> > No, it does not.  You can test it by shutting down X11 (try:
> > "/etc/init.d/xserver-nodm stop"); this will also terminate the
> > dbus-launch process, and your login shell immediately works fine.
> >
> > Or try out the patch I posted.
> >
> >> What I haven't been able to explain yet is why just omitting the getty
> >> from the tty doesn't result in console on the serial port due to the
> >> kernel's automatic console thing. So clearly there are some gaps in my
> >> explanation here, but please try this approach and let me know what your
> >> results are. Based on that, we can dig a bit more and figure out how to
> >> best setup the console= directives on the default images.
> >
> > THere is no problem with the console= settings.  It's two processes
> > reading from a single input stream. This can never work.  Try it ut if
> > you don't believe me.
> 
> Wolfgang has it spot-on - both the console login and dbus are
> fighting over the console device.
> 
> I've been using the equivalent of this patch for months and it
> solves the problem just fine.  (Sorry I didn't report it, it
> wasn't high on my list)

FWIW I've now merged Wolfgang's patch into master.

If there are issues like this please do tell us about them as its good
to get them fixed.

Cheers,

Richard