perf: Fix context leak in put_event()

perf: Fix context leak in put_event()

Commit:

  a83fe28e2e45 ("perf: Fix put_event() ctx lock")

changed the locking logic in put_event() by replacing mutex_lock_nested()
with perf_event_ctx_lock_nested(), but didn't fix the subsequent
mutex_unlock() with a correct counterpart, perf_event_ctx_unlock().

Contexts are thus leaked as a result of incremented refcount
in perf_event_ctx_lock_nested().

Signed-off-by: Leon Yu <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Fixes: a83fe28e2e45 ("perf: Fix put_event() ctx lock")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>