from Bjoern Doebel :
> Are you just having a problem understanding the observed values or is there
> a real problem that you are running into? If the latter, could you provide
> a small example program so that we can reproduce it here?
That's a real problem. I use several producer (08 and others) and one
consumer (03) around a queue. I observed state 4, 5 and 6. This is
anoying because semaphore_down exits as my queue is empty. At the
begining I looked for some memory overflow into my code... But I found
the scenario above which could explain this strange state.
I tried a little change into archindep.h and the problem doesn't
appear anymore. However, I find it very dirty and uncomplete because
asm.h and generic should be also changed. As I don't know very well
semaphore, maybe there are some case broken ?
Marc
--- include/archindep.h (revision 230)
+++ include/archindep.h (working copy)
@@ -54,7 +54,7 @@
L4_INLINE int
l4semaphore_down_timed(l4semaphore_t * sem, unsigned timeout)
{
- int old,tmp,ret;
+ int old,pending,tmp,ret;
l4_umword_t dummy;
l4_msgdope_t result;
@@ -66,6 +66,7 @@
do
{
old = sem->counter;
+ pending = sem->pending
tmp = old - 1;
}
/* retry if someone else also modified the counter */
@@ -73,7 +74,7 @@
(l4_uint32_t)old, (l4_uint32_t)tmp));
- if (tmp < 0)
+ if (pending || (tmp < 0))
{
/* we did not get the semaphore, block */
ret = l4_ipc_call(l4semaphore_thread_l4_id,
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