On 21/10/15 15:48, Jay Doyle wrote:
On 10/21/2015 09:35 AM, Sebastian Huber wrote:
On 21/10/15 15:08, Isaac Gutekunst wrote:
On 10/21/2015 09:00 AM, Sebastian Huber wrote:
On 21/10/15 14:56, Isaac Gutekunst wrote:
On 10/21/2015 08:24 AM, Sebastian Huber wrote:
On 21/10/15 14:13, Isaac Gutekunst wrote:
Thanks for the reply.
On 10/21/2015 01:50 AM, Sebastian Huber wrote:
On 20/10/15 16:02, Isaac Gutekunst wrote:
[...]
As far as I can tell this would only occur if the caller of
pthread_mutex_lock was in a
"bad"
state. I don't believe it is in an interrupt context, and
don't know what other bad states
could exist.
We have
#define _CORE_mutex_Check_dispatch_for_seize(_wait) \
(!_Thread_Dispatch_is_enabled() \
&& (_wait) \
&& (_System_state_Get() >= SYSTEM_STATE_UP))
What is the thread dispatch disable level and the system state
at this point?
In case the thread dispatch disable level is not zero, then
something is probably broken
in the
operating system code which is difficult to find. Could be a
general memory corruption
problem
too. Which RTEMS version do you use?
The thread dispatch disable level is usually -1 or -2.
(0xFFFFFFFE or 0xFFFFFFD).
A negative value is very bad, but easy to detect via manual
instrumentation (only an hand full
of spots touch this variable) or hardware
breakpoints/watchpoints. Looks the rest of
_Per_CPU_Information all right?
It looks like it's only the thread_dispatch_disable_level that's
broken.
We'll go and grep for all places for all the places it's touched,
and look for something.
The problem with watchpoints is they fire exceptionally often, and
putting in a conditional
watchpoint slows the code to a crawl, but that may be worth it.
Here are some printouts of the relevant structs right after a crash:
$4 = {
cpu_per_cpu = {<No data fields>},
isr_nest_level = 0,
thread_dispatch_disable_level = 4294967295,
executing = 0xc01585c8,
heir = 0xc0154038,
dispatch_necessary = true,
time_of_last_context_switch = {
sec = 2992,
frac = 10737447432380511034
},
Stats = {<No data fields>}
}
No, this doesn't look good. According to the stack trace you are in
thread context. However, we
have executing != heir and dispatch_necessary == true. This is a
broken state itself. I guess,
something is wrong with the interrupt level so that a context
switch is blocked. On ARMv7-M
this is done via the system call exception.
This is a bit beyond my RTEMS knowledge. What would you advise
looking into?
I would try to instrument the code to figure out where the thread
dispatch disable level goes negative.
We just did. I added a check in _ARMV7M_Interrupt_service_leave to
see if the _Thread_Dispatch_disable_level is positive before the
decrementing it and this eventually fails.
I'm not sure if this tells us much because I think the call itself
correct. In this particular case it is processing an I2C interrupt.
I will try to see if we can capture information about the sequence of
changes to the _Thread_Dispatch_disable_level just before the point in
which we know something is clearly wrong (i.e., decreasing it below
zero.)
Since the isr_nest_level is 0, I don't think its a problem with the
spots that use _ARMV7M_Interrupt_service_leave(). Did you check the
interrupt priorities? See also
https://lists.rtems.org/pipermail/users/2015-June/029155.html
--
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.hu...@embedded-brains.de
PGP : Public key available on request.
Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
_______________________________________________
devel mailing list
devel@rtems.org
http://lists.rtems.org/mailman/listinfo/devel
