GDB does not step into or over "sleep" function

GDB does not step into or over "sleep" function

[Denset.Serralta]

We are using GDB 4.18 on an NT host to debug target software running on a
PowerPC based adapter. We are using a function called ProcessSleep which is
a call to our kernel.  It basically allocates a semaphore, blocks on it
subject to a user specified timeout and then returns the semaphore.One
problem we can't seem to get around though is that if the process being
debugged makes a 'ProcessSleep' call, the debugger never gains control when
we step over it.  Even if we set a breakpoint past the call and let it run,
it never returns.  A status utility that we have shows the process as
queued, but we never regain control.  Does anybody know any reason(s) why
this should happen.

Re: GDB does not step into or over "sleep" function

[Jim Blandy]

Denset.Serralta@radisys.com writes:
> We are using GDB 4.18 on an NT host to debug target software running on a
> PowerPC based adapter. We are using a function called ProcessSleep which is
> a call to our kernel.  It basically allocates a semaphore, blocks on it
> subject to a user specified timeout and then returns the semaphore.One
> problem we can't seem to get around though is that if the process being
> debugged makes a 'ProcessSleep' call, the debugger never gains control when
> we step over it.  Even if we set a breakpoint past the call and let it run,
> it never returns.  A status utility that we have shows the process as
> queued, but we never regain control.  Does anybody know any reason(s) why
> this should happen.

Let me make sure I understand.  If you have code like this:

    ... some code ...
    ProcessSleep (...);
    ... some more code ...

and you set a breakpoint on the `some more code' line, your program
hangs and never reaches the breakpoint.

But if you run the program without GDB, it sleeps the expected amount
of time, and then continues normally.

Is that right?

Re: GDB does not step into or over "sleep" function

[Denset.Serralta]

                                                                                                                        
                    Jim Blandy                                                                                          
                    <jimb@zwingli.cygn        To:     Denset.Serralta@radisys.com                                       
                    us.com>                   cc:     gdb@sources.redhat.com                                            
                    Sent by:                  Subject:     Re: GDB does not step into or over "sleep" function          
                    gdb-owner@sources.                                                                                  
                    redhat.com                                                                                          
                                                                                                                        
                                                                                                                        
                    11/28/00 08:07 PM                                                                                   
                                                                                                                        
                                                                                                                        






Jim Blandy wrote:
>Let me make sure I understand.  If you have code like this:
>
>    ... some code ...
>    ProcessSleep (...);
>    ... some more code ...
>
>and you set a breakpoint on the `some more code' line, your program
>hangs and never reaches the breakpoint.

>But if you run the program without GDB, it sleeps the expected amount
>of time, and then continues normally.


Thanks for responding

You are correct. The breakpoint in  "...some more code ..." is never
reached. We are suspecting
at the moment that it is a problem with the ProcessSleep function since the
hang occurrs when we
'step into' or 'step over' it. What we don't know is whether it is a
problem with our underlying kernel
functions or whether GDB has a problem with a "sleep" function which
allocates a semaphore,
blocks on it subject to a user specified timeout and then returns the
semaphore. We are leaning
to suspecting that it is a problem with our custom kernel (i.e. GDB is
innocent). However I thought
I would ask the GDB group, with all the combined experience developing GDB,
just in case they
saw something obvious.

Thanks again
Denset.Serralta@radisys.com


>Denset.Serralta@radisys.com writes:
>> We are using GDB 4.18 on an NT host to debug target software running on
a
>> PowerPC based adapter. We are using a function called ProcessSleep which
is
>> a call to our kernel.  It basically allocates a semaphore, blocks on it
>> subject to a user specified timeout and then returns the semaphore.One
>> problem we can't seem to get around though is that if the process being
>> debugged makes a 'ProcessSleep' call, the debugger never gains control
when
>> we step over it.  Even if we set a breakpoint past the call and let it
run,
>> it never returns.  A status utility that we have shows the process as
>> queued, but we never regain control.  Does anybody know any reason(s)
why
>> this should happen.

Re: GDB does not step into or over "sleep" function

[Jim Blandy]

> You are correct. The breakpoint in  "...some more code ..." is never
> reached. We are suspecting
> at the moment that it is a problem with the ProcessSleep function since the
> hang occurrs when we
> 'step into' or 'step over' it. What we don't know is whether it is a
> problem with our underlying kernel
> functions or whether GDB has a problem with a "sleep" function which
> allocates a semaphore,
> blocks on it subject to a user specified timeout and then returns the
> semaphore. We are leaning
> to suspecting that it is a problem with our custom kernel (i.e. GDB is
> innocent). However I thought
> I would ask the GDB group, with all the combined experience developing GDB,
> just in case they
> saw something obvious.

Yes, this sounds like a bug in the OS.  Or perhaps your GDB stub is
interfering with some interrupt handling needed to implement
ProcessSleep.