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Subject: Re: [OMPI devel] callback debugging
From: Adrian Reber (adrian_at_[hidden])
Date: 2014-01-21 10:24:18


I think I still do not really understand how it works.

The barrier on which orte-checkpoint is currently hanging is in
app_coord_init(). You are also saying that orte-checkpoint
should not be calling a barrier. The backtrace of the point where it
is hanging now looks like:

#0 0x00007ffff69befa0 in __nanosleep_nocancel () at ../sysdeps/unix/syscall-template.S:81
#1 0x00007ffff7b45712 in app_coord_init () at ../../../../../orte/mca/snapc/full/snapc_full_app.c:208
#2 0x00007ffff7b3a5ce in orte_snapc_full_module_init (seed=false, app=true) at ../../../../../orte/mca/snapc/full/snapc_full_module.c:207
#3 0x00007ffff7b375de in orte_snapc_base_select (seed=false, app=true) at ../../../../orte/mca/snapc/base/snapc_base_select.c:96
#4 0x00007ffff7a9884a in orte_ess_base_tool_setup () at ../../../../orte/mca/ess/base/ess_base_std_tool.c:192
#5 0x00007ffff7a9fe85 in rte_init () at ../../../../../orte/mca/ess/tool/ess_tool_module.c:83
#6 0x00007ffff7a4647f in orte_init (pargc=0x7fffffffd94c, pargv=0x7fffffffd940, flags=8) at ../../orte/runtime/orte_init.c:158
#7 0x0000000000402859 in ckpt_init (argc=51, argv=0x7fffffffda78) at ../../../../orte/tools/orte-checkpoint/orte-checkpoint.c:610
#8 0x0000000000401d7a in main (argc=51, argv=0x7fffffffda78) at ../../../../orte/tools/orte-checkpoint/orte-checkpoint.c:245

Maybe I am doing something completely wrong. I am currently
running 'orterun -np 2 test-programm'.

In another terminal I am starting orte-checkpoint with the PID of
orterun and the barrier in app_coord_init() is just before it tries
to communicate with orterun. Is this the correct setup?

                Adrian

On Mon, Jan 20, 2014 at 05:33:59PM -0600, Josh Hursey wrote:
> If it is the application, then there is probably a barrier in the
> app_coord_init() to make sure all the applications are up and running.
> After this point then the global coordinator knows that the application can
> be checkpointed.
>
> I don't think orte-checkpoint should be calling a barrier - from what I
> recall.
>
>
> On Mon, Jan 20, 2014 at 4:46 PM, Ralph Castain <rhc_at_[hidden]> wrote:
>
> > Is it orte-checkpoint that is hanging, or the app you are trying to
> > checkpoint?
> >
> >
> > On Jan 20, 2014, at 2:10 PM, Adrian Reber <adrian_at_[hidden]> wrote:
> >
> > Thanks for your help. I tried initializing the barrier correctly (see
> > attached patch) but now, instead of crashing, it just hangs on the
> > barrier while running orte-checkpoint
> >
> > [dcbz:20150] [[41665,0],0] grpcomm:bad entering barrier
> > [dcbz:20150] [[41665,0],0] ACTIVATING GRCPCOMM OP 0 at
> > ../../../../../orte/mca/grpcomm/bad/grpcomm_bad_module.c:206
> >
> > #0 0x00007ffff69befa0 in __nanosleep_nocancel () at
> > ../sysdeps/unix/syscall-template.S:81
> > #1 0x00007ffff7b456ba in app_coord_init () at
> > ../../../../../orte/mca/snapc/full/snapc_full_app.c:207
> > #2 0x00007ffff7b3a582 in orte_snapc_full_module_init (seed=false,
> > app=true) at ../../../../../orte/mca/snapc/full/snapc_full_module.c:207
> >
> > it hangs looping at ORTE_WAIT_FOR_COMPLETION(coll->active);
> >
> > I do not understand on what the barrier here is actually waiting for. Where
> > do I need to look to find the place the barrier is waiting for?
> >
> > I also tried initializing the collective id's in
> > orte/mca/plm/base/plm_base_launch_support.c but that code is never
> > used running the orte-checkpoint tool
> >
> > Adrian
> >
> > On Sat, Jan 11, 2014 at 11:46:42AM -0800, Ralph Castain wrote:
> >
> > I took a look at this, and I'm afraid you have some work to do in the
> > orte/mca/snapc code base:
> >
> > 1. you must use dynamically allocated buffers for rml.send_buffer_nb. See
> > r30261 for an example of the changes that need to be made - I did some, but
> > can't swear to catching them all. It was enough to at least get a proc past
> > the initial snapc registration
> >
> > 2. you are reusing collective id's to execute several orte_grpcomm.barrier
> > calls - those ids are used elsewhere during MPI_Init. This is not allowed -
> > a collective id can only be used *once*. What you need to do is go into
> > orte/mca/plm/base/plm_base_launch_support.c and (when cr is configured) add
> > cr-specific collective id's for this purpose. I don't know how many places
> > in the cr code create their own barriers, but they each need a collective
> > id.
> >
> > If you prefer and have the time, you are welcome to extend the collective
> > code to allow id reuse. This would require that each daemon and app "reset"
> > the collective fields when a collective is declared complete. It isn't that
> > hard to do - just never had a reason to do it. I can take a shot at it when
> > time permits (may have some time this weekend)
> >
> > 3. when you post the non-blocking recv in the snapc/full code, it looks to
> > me like you need to block until you get the answer. I don't know where in
> > the code flow this is occurring - if you are not in an event, then it is
> > okay to block using ORTE_WAIT_FOR_COMPLETION. Look in
> > orte/mca/routed/base/routed_base_fns.c starting at line 252 for an example.
> >
> > HTH
> > Ralph
> >
> > On Jan 10, 2014, at 12:55 PM, Ralph Castain <rhc_at_[hidden]> wrote:
> >
> >
> > On Jan 10, 2014, at 12:45 PM, Adrian Reber <adrian_at_[hidden]> wrote:
> >
> > On Fri, Jan 10, 2014 at 09:48:14AM -0800, Ralph Castain wrote:
> >
> >
> > On Jan 10, 2014, at 8:02 AM, Adrian Reber <adrian_at_[hidden]> wrote:
> >
> > I am currently trying to understand how callbacks are working. Right now
> > I am looking at orte/mca/rml/base/rml_base_receive.c
> > orte_rml_base_comm_start() which does
> >
> > orte_rml.recv_buffer_nb(ORTE_NAME_WILDCARD,
> > ORTE_RML_TAG_RML_INFO_UPDATE,
> > ORTE_RML_PERSISTENT,
> > orte_rml_base_recv,
> > NULL);
> >
> > As far as I understand it orte_rml_base_recv() is the callback function.
> > At which point should this function run? When the data is actually
> > received?
> >
> >
> > Not precisely. When data is received by the OOB, it pushes the data into
> > an event. When that event gets serviced, it calls the orte_rml_base_receive
> > function which processes the data to find the matching tag, and then uses
> > that to execute the callback to the user code.
> >
> >
> > The same for send_buffer_nb() functions. I do not see the callback
> > functions actually running. How can I verify that the callback functions
> > are running. Especially for the send case it sounds pretty obvious how
> > it should work but I never see the callback function running. At least
> > in my setup.
> >
> >
> > The data is not immediately sent. It gets pushed into an event. When that
> > event gets serviced, it calls the orte_oob_base_send function which then
> > passes the data to each active OOB component until one of them says it can
> > send it. The data is then pushed into another event to get it into the
> > event base for that component's active module - when that event gets
> > serviced, the data is sent. Once the data is sent, an event is created
> > that, when serviced, executes the callback to the user code.
> >
> > If you aren't seeing callbacks, the most likely cause is that the orte
> > progress thread isn't running. Without it, none of this will work.
> >
> >
> > Thanks. Running configure without '--with-ft=cr' I can run a program and
> > use orte-top. In orterun I can see that the callback is running and
> > orte-top displays the retrieved information. I can also see in orte-top
> > that the callbacks are working.
> >
> >
> > Actually, I'm rather impressed - I hadn't tested orte-top and didn't
> > honestly know if it would work any more! Glad to hear it does :-)
> >
> > Doing the same with '--with-ft=cr'
> > enabled orte-top crashes as well as orte-checkpoint and both (-top and
> > -checkpoint) seem to no longer have working callbacks and that is why
> > they are probably crashing. So some code which is enabled by '--with-ft=cr'
> > seems to break callbacks in orte-top as well as in orte-checkpoint.
> > orterun handles callbacks no matter if configured with or without
> > '--with-ft=cr'.
> >
> >
> > I can take a look this weekend - probably something silly
> >
> >
> > Adrian
> >
> > <grpcomm.txt>_______________________________________________
> >
> > devel mailing list
> > devel_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
> >
> >
> >
> > _______________________________________________
> > devel mailing list
> > devel_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
> >
>
>
>
> --
> Joshua Hursey
> Assistant Professor of Computer Science
> University of Wisconsin-La Crosse
> http://cs.uwlax.edu/~jjhursey

> _______________________________________________
> devel mailing list
> devel_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/devel

                Adrian

-- 
Adrian Reber <adrian_at_[hidden]>            http://lisas.de/~adrian/
QOTD:
	"I tried buying a goat instead of a lawn tractor; had to return
	it though.  Couldn't figure out a way to connect the snow blower."