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Re: Two threads -two messages - one mbox
- From: Bart Veer <bartv at ecoscentric dot com>
- To: gorjup at norik dot com
- Cc: ecos-discuss at sources dot redhat dot com
- Date: Sun, 20 Jun 2004 18:32:14 +0100 (BST)
- Subject: Re: [ECOS] Two threads -two messages - one mbox
- References: <200406201844.40331.gorjup@norik.com>
>>>>> "Matthias" == Matthias Gorjup <gorjup@norik.com> writes:
Matthias> Hello,
Matthias> I am having problems with sending more than on
Matthias> mbox-meassage in one loop-iteration from one thread to
Matthias> another. Below is the code we are using:
<snip>
Matthias> If I only send one message and read one mesage, the code
Matthias> works fine. But if I send two messages in one iteration,
Matthias> the system reboots after the first iteration of the
Matthias> sending thread.
Matthias> I must say that I need to send two integer values from
Matthias> one thread to another during one iteration and the other
Matthias> thread needs to read both of them in one iteration as
Matthias> well.
Matthias> What could be wrong?
Matthias> Should I use a global structure with two integer
Matthias> elements and then send only a pointer to that structure
Matthias> (this would make it possible to send only one message in
Matthias> one iteration)? Should I use mutex-es or some other
Matthias> synchronizaiton mechanism?
I can see two obvious problems with your code.
1) you are creating and starting the threads before the
synchronization data structures. In particular mbox_handle could
get used by thread1() or thread2() before main() has created it. In
your simple example code main() is likely to run at a higher
priority then the other threads so there is not actually a problem,
but that is likely to change as the code gets more complicated. It
is a good idea to initialize all synchronization data structures
before starting any threads.
2) you are not allocating any space for the mbox itself. Your sock_msb
argument to cyg_mbox_create() is an uninitialized pointer so it
will have a value of 0. Hence you are placing the mbox at location
0, where the interrupt vectors are likely to be depending on the
architecture you are using.
I suspect that when you do the second mbox send you are overwriting
a critical interrupt vector, and the next time an interrupt
triggers the system will crash and burn.
Instead you need to allocate space for the mbox, something like:
cyg_handle_t mbox_handle;
cyg_mbox mbox_data;
...
int
main(int argc, char** argv)
{
cyg_mbox_create(&mbox_handle, &mbox_data);
/* now create and start the threads */
}
Bart
--
Bart Veer eCos Configuration Architect
http://www.ecoscentric.com/ The eCos and RedBoot experts
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