Hi list,
I'm simultaneously happy and embarrassed to present a possible fix,
which I have tested about 3 times only.
My suspicions are one of the following is true (certainly the last):
- thread 2's stack isn't being allocated correctly somehow
Yep, thread 2's stack was being allocated to 16k, same as RTAI, but when
hit with the great (as in size) glibc, it broke. I upped the stack to
4MB and latency-test runs perfectly. This should be tuned down of
course, and there's an option in configure.in to use dietlibc that will
allow it to be tuned down even further.
Suggestions for how to go about tuning?
- I'm still clueless and need to do a bunch more reading. :P
Yep. Embarrassing that it took breaking out all the heavy tools to find
what should've been obvious. At least the hit in my pride is greatly
outweighed by my new huge tool belt!
If this fix is confirmed to work, then I'll make good on the bounty!
John
commit 4c0e4ddef8337c47ab998257e98260204f2340ac
Author: John Morris <j...@zultron.com>
Date: Fri May 4 15:57:16 2012 -0500
Increase HAL_STACKSIZE (thread stacksize) for PREEMPT_RT to stop segfaults
The previous 16k stacksize is fine for kernel modules, but much too small
for PREEMPT_RT, which uses libc.
This number, 4MB, is probably way too large, and should be tuned. There's
also the possibility for using dietlibc in configure.in, which may allow
the number to be reduced even further.
For now, I'm just happy the thing runs!
diff --git a/src/hal/hal_priv.h b/src/hal/hal_priv.h
index 1ef1f74..686d781 100644
--- a/src/hal/hal_priv.h
+++ b/src/hal/hal_priv.h
@@ -287,7 +287,11 @@ typedef struct {
int funct_ptr; /* pointer to function */
} hal_funct_entry_t;
-#define HAL_STACKSIZE 16384 /* realtime task stacksize */
+#ifdef RTAPI_LINUX
+#define HAL_STACKSIZE 4194304 /* realtime task stacksize for PREEMPT_RT */
+#else
+#define HAL_STACKSIZE 16384 /* realtime task stacksize for RTAI (RT-Linux?) */
+#endif
typedef struct {
int next_ptr; /* next thread in linked list */
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