Stefan Hajnoczi writes:
> AFAICT the only problem with libust is the __tp_cb_data set but not
> used warning that gcc 4.6 emits, see my test program:
Here's a prettified version of the failing (pre-processed) code:
static inline
void
trace_ust_g_malloc(size_t size, void* ptr)
{
do {
if (__builtin_expect(!!(__tracepoint_ust_g_malloc.state), 0))
do {
struct tracepoint_probe *__tp_it_probe_ptr;
void *__tp_it_func;
void *__tp_cb_data;
rcu_read_lock_bp();
__tp_it_probe_ptr = ({
typeof((&__tracepoint_ust_g_malloc)->probes) _________p1 =
rcu_dereference_sym((void *)((&__tracepoint_ust_g_malloc)->probes));
(_________p1); });
if (__tp_it_probe_ptr) {
do {
__tp_it_func = __tp_it_probe_ptr->func;
__tp_cb_data = __tp_it_probe_ptr->data;
((void(*)(size_t size, void* ptr))__tp_it_func)(size,
ptr);
} while ((++__tp_it_probe_ptr)->func); }
rcu_read_unlock_bp();
} while (0);
} while (0);
}
Which is produced by the "__DO_TRACE" macro in "ust/tracepoint.h". The original
code is:
DECLARE_TRACE(ust_g_malloc, TP_PROTO(size_t size, void* ptr), TP_ARGS(size,
ptr));
#define trace_g_malloc trace_ust_g_malloc
I don't know about the portability requirements in UST, but if supporting only
gcc is an option, you can simply use this line in the macro:
void *__tp_cb_data __attribute__((unused));
Even with this fixed, there still seem to be problems with events without
parameters:
DECLARE_TRACE(ust_slavio_misc_update_irq_raise, TP_PROTO(void), TP_ARGS());
#define trace_slavio_misc_update_irq_raise
trace_ust_slavio_misc_update_irq_raise
./trace.h: In function ‘__trace_ust_slavio_misc_update_irq_raise’:
./trace.h:361:1: error: ‘void’ must be the only parameter
./trace.h:361:1: error: expected expression before ‘)’ token
./trace.h:361:1: error: too many arguments to function ‘(void (*)(void
*))__tp_it_func’
The debian/testing version of ust is 0.15, and the sources have a ChangeLog with
this at the top:
2011-07-15 ust 0.15
* Add backward compability for tracepoint API (still planned for
deprecation, but should make the transition smoother).
Lluis
--
"And it's much the same thing with knowledge, for whenever you learn
something new, the whole world becomes that much richer."
-- The Princess of Pure Reason, as told by Norton Juster in The Phantom
Tollbooth
