[En-Nut-Discussion] Handling of condition variables broken?
phip at hb9etc.ch
Thu Dec 27 22:56:45 CET 2012
today I needed to do some thread synchronization, which I'd liked to do
using a condition variable. But there are a few problems with this.
First, have a look at the implementation of the init function:
int NutConditionInit( CONDITION * cond)
cond = NutHeapAlloc(sizeof(struct _CONDITION));
if (cond == NULL) return 1;
Given the CONDITION declaration as
typedef struct _CONDITION CONDITION;
this will not work. NutHeapAlloc() may happily allocate memory and store
it into cond, but there is no way to find out where the memory region is
located. Either it should be returned as a pointer or the function must
take a double pointer as argument.
Then there's NutConditionTimedWait() which advertises its return value
as "0 on success, -1 on error or timeout". But:
int NutConditionTimedWait(CONDITION * cond, uint32_t abs_ms)
if (cond == NULL) return -1;
ms = abs_ms - NutGetMillis();
if (ms > 0x7FFFFFFF) return -1;
A timeout will never cause the function to return -1. Additionally, this
function is missing in the header file <sys/condition.h>. The example in
the doxygen doc is also extremely outdated.
Could it be that there has been the idea to restructure some of this
module but it was never finished?
Anyway, I'll change my code to use bare event queues instead. But this
code should either be corrected or removed.
Thanks and best regards,
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