27c68c216e
On SPR, the load latency event needs an auxiliary event in the same
group to work properly. There's a check in intel_pmu_hw_config()
for this to iterate sibling events and find a mem-loads-aux event.
The for_each_sibling_event() has a lockdep assert to make sure if it
disabled hardirq or hold leader->ctx->mutex. This works well if the
given event has a separate leader event since perf_try_init_event()
grabs the leader->ctx->mutex to protect the sibling list. But it can
cause a problem when the event itself is a leader since the event is
not initialized yet and there's no ctx for the event.
Actually I got a lockdep warning when I run the below command on SPR,
but I guess it could be a NULL pointer dereference.
$ perf record -d -e cpu/mem-loads/uP true
The code path to the warning is:
sys_perf_event_open()
perf_event_alloc()
perf_init_event()
perf_try_init_event()
x86_pmu_event_init()
hsw_hw_config()
intel_pmu_hw_config()
for_each_sibling_event()
lockdep_assert_event_ctx()
We don't need for_each_sibling_event() when it's a standalone event.
Let's return the error code directly.
Fixes:
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|---|---|---|
| .. | ||
| amd | ||
| intel | ||
| zhaoxin | ||
| Kconfig | ||
| Makefile | ||
| core.c | ||
| msr.c | ||
| perf_event.h | ||
| perf_event_flags.h | ||
| probe.c | ||
| probe.h | ||
| rapl.c | ||
| utils.c | ||