[ECOS] Problem with CPU Load Measurements and gcc-arm-eabi optimization.

lesc lesc@zhaw.ch
Mon Nov 17 13:06:00 GMT 2014


Hello Everyone

I just encountered the Problem that the cyg_cpuload_create always 
delivers 100% on my System. After a bit of debugging I figured out, that 
the whole for-loop in idle_thread_main seems to be omitted.

I could fix this Problem with declaring 
idle_thread_loops[CYGNUM_KERNEL_CPU_MAX] as volatile (patch below). But 
this has maybe some consequences I am not thinking of, as the variables 
are now always synced to the ram and no kept in a CPU register.

Do you see any Problem with my approach?

Regards Serafin

Patch:

 From 2799f68a5e508c6bece6ec85b1e201282983b98d Mon Sep 17 00:00:00 2001
From: Serafin Leschke <lesc@zhaw.ch>
Date: Mon, 17 Nov 2014 13:51:23 +0100
Subject: [PATCH] declare idle_thread_loops as volatile

---
  packages/kernel/current/src/common/thread.cxx | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/kernel/current/src/common/thread.cxx 
b/packages/kernel/current/src/common/thread.cxx
index 86a3dc4..bd1aa99 100644
--- a/packages/kernel/current/src/common/thread.cxx
+++ b/packages/kernel/current/src/common/thread.cxx
@@ -1211,7 +1211,7 @@ Cyg_ThreadTimer::alarm(
  #endif // CYGNUM_HAL_STACK_SIZE_MINIMUM

  // Loop counter for debugging/housekeeping
-cyg_uint32 idle_thread_loops[CYGNUM_KERNEL_CPU_MAX];
+volatile cyg_uint32 idle_thread_loops[CYGNUM_KERNEL_CPU_MAX];

  static char 
idle_thread_stack[CYGNUM_KERNEL_CPU_MAX][CYGNUM_KERNEL_THREADS_IDLE_STACK_SIZE];

-- 
1.9.1


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