[PATCH] D38995: [XRay][compiler-rt] Always place the CPU record first for every buffer

[Dean Michael Berris via Phabricator via llvm-commits]

dberris created this revision.

In FDR Mode, when we set up a new buffer for a thread that's just
overflowed, we must place the CPU identifier with the TSC record as the
first record. This is so that we can reconstruct all the function
entry/exit with deltas rooted on a TSC record for the CPU at the
beginning of the buffer.

Without doing this, the tools are rejecting the log for cases when we've
overflown and have different buffers that don't have the CPU and TSC
records as the first entry in the buffers.


https://reviews.llvm.org/D38995

Files:
  lib/xray/xray_fdr_logging.cc
  lib/xray/xray_fdr_logging_impl.h


Index: lib/xray/xray_fdr_logging_impl.h
===================================================================
--- lib/xray/xray_fdr_logging_impl.h
+++ lib/xray/xray_fdr_logging_impl.h
@@ -532,7 +532,8 @@
   return true;
 }
 
-inline bool prepareBuffer(int (*wall_clock_reader)(clockid_t,
+inline bool prepareBuffer(uint64_t TSC, unsigned char CPU,
+                          int (*wall_clock_reader)(clockid_t,
                                                    struct timespec *),
                           size_t MaxSize) XRAY_NEVER_INSTRUMENT {
   auto &TLD = getThreadLocalData();
@@ -549,6 +550,9 @@
       return false;
     }
     setupNewBuffer(wall_clock_reader);
+
+    // Always write the CPU metadata as the first record in the buffer.
+    writeNewCPUIdMetadata(CPU, TSC);
   }
   return true;
 }
@@ -599,6 +603,9 @@
     }
 
     setupNewBuffer(wall_clock_reader);
+
+    // Always write the CPU metadata as the first record in the buffer.
+    writeNewCPUIdMetadata(CPU, TSC);
   }
 
   if (TLD.CurrentCPU == std::numeric_limits<uint16_t>::max()) {
@@ -728,7 +735,7 @@
   // bytes in the end of the buffer, we need to write out the EOB, get a new
   // Buffer, set it up properly before doing any further writing.
   size_t MaxSize = FunctionRecSize + 2 * MetadataRecSize;
-  if (!prepareBuffer(wall_clock_reader, MaxSize)) {
+  if (!prepareBuffer(TSC, CPU, wall_clock_reader, MaxSize)) {
     TLD.LocalBQ = nullptr;
     return;
   }
Index: lib/xray/xray_fdr_logging.cc
===================================================================
--- lib/xray/xray_fdr_logging.cc
+++ lib/xray/xray_fdr_logging.cc
@@ -206,17 +206,17 @@
 void fdrLoggingHandleArg0(int32_t FuncId,
                           XRayEntryType Entry) XRAY_NEVER_INSTRUMENT {
   auto TSC_CPU = getTimestamp();
-  __xray_fdr_internal::processFunctionHook(
-      FuncId, Entry, std::get<0>(TSC_CPU), std::get<1>(TSC_CPU), 0,
-      clock_gettime, *BQ);
+  __xray_fdr_internal::processFunctionHook(FuncId, Entry, std::get<0>(TSC_CPU),
+                                           std::get<1>(TSC_CPU), 0,
+                                           clock_gettime, *BQ);
 }
 
 void fdrLoggingHandleArg1(int32_t FuncId, XRayEntryType Entry,
                           uint64_t Arg) XRAY_NEVER_INSTRUMENT {
   auto TSC_CPU = getTimestamp();
-  __xray_fdr_internal::processFunctionHook(
-      FuncId, Entry, std::get<0>(TSC_CPU), std::get<1>(TSC_CPU), Arg,
-      clock_gettime, *BQ);
+  __xray_fdr_internal::processFunctionHook(FuncId, Entry, std::get<0>(TSC_CPU),
+                                           std::get<1>(TSC_CPU), Arg,
+                                           clock_gettime, *BQ);
 }
 
 void fdrLoggingHandleCustomEvent(void *Event,
@@ -248,7 +248,7 @@
   //   - The metadata record we're going to write. (16 bytes)
   //   - The additional data we're going to write. Currently, that's the size of
   //   the event we're going to dump into the log as free-form bytes.
-  if (!prepareBuffer(clock_gettime, MetadataRecSize + EventSize)) {
+  if (!prepareBuffer(TSC, CPU, clock_gettime, MetadataRecSize + EventSize)) {
     TLD.LocalBQ = nullptr;
     return;
   }


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