x86, perf_counter, bts: Fail if BTS is not available
Reserve PERF_COUNT_HW_BRANCH_INSTRUCTIONS with sample_period ==
1 for BTS tracing and fail, if BTS is not available.
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20090902140612.943801000@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 396e35d..2f41874 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -769,7 +769,7 @@
int cpu, err = 0;
if (!bts_available())
- return -EOPNOTSUPP;
+ return 0;
get_online_cpus();
@@ -914,7 +914,7 @@
if (!reserve_pmc_hardware())
err = -EBUSY;
else
- reserve_bts_hardware();
+ err = reserve_bts_hardware();
}
if (!err)
atomic_inc(&active_counters);
@@ -979,6 +979,13 @@
if (config == -1LL)
return -EINVAL;
+ /*
+ * Branch tracing:
+ */
+ if ((attr->config == PERF_COUNT_HW_BRANCH_INSTRUCTIONS) &&
+ (hwc->sample_period == 1) && !bts_available())
+ return -EOPNOTSUPP;
+
hwc->config |= config;
return 0;
@@ -1355,19 +1362,9 @@
idx = fixed_mode_idx(counter, hwc);
if (idx == X86_PMC_IDX_FIXED_BTS) {
- /*
- * Try to use BTS for branch tracing. If that is not
- * available, try to get a generic counter.
- */
- if (unlikely(!cpuc->ds))
- goto try_generic;
-
- /*
- * Try to get the fixed counter, if that is already taken
- * then try to get a generic counter:
- */
+ /* BTS is already occupied. */
if (test_and_set_bit(idx, cpuc->used_mask))
- goto try_generic;
+ return -EAGAIN;
hwc->config_base = 0;
hwc->counter_base = 0;