commit d6b4b44bad078fb647d01b13a2f39b9ddcaa61b3
author Yabin Cui <yabinc@google.com> Mon Dec 20 21:17:37 2021 -0800
committer Yabin Cui <yabinc@google.com> Tue Dec 21 10:59:59 2021 -0800
tree f28bc5a0b00c21ac4d66728a7cb2d193950bb015
parent 246012654f77bf07ab231fdda503198c6c25f9c7

simpleperf: use ioctl to get event fd id.

Currently EventFd uses read() to get id. But it
is affected by event_attr.read_format, which will
change based on record options. So switch to get id
via ioctl.

Bug: 211001523
Test: run simpleperf_unit_test
Change-Id: I4beb9865e357aa77c2522d5a2688b925cbb793e2

simpleperf/event_fd.cpp

diff --git a/simpleperf/event_fd.cpp b/simpleperf/event_fd.cpp
index 0343e15..1afc162 100644
--- a/simpleperf/event_fd.cpp
+++ b/simpleperf/event_fd.cpp
@@ -101,9 +101,8 @@
 
 uint64_t EventFd::Id() const {
   if (id_ == 0) {
-    PerfCounter counter;
-    if (InnerReadCounter(&counter)) {
-      id_ = counter.id;
+    if (ioctl(perf_event_fd_, PERF_EVENT_IOC_ID, &id_) != 0) {
+      PLOG(WARNING) << "failed to get id of event_fd";
     }
   }
   return id_;