[XRay][compiler-rt] Use a single global volatile recursion guard for FDR handlers

Summary:
Before this change, the recursion guard for the flight data recorder
(FDR) mode handlers were independent. This change makes it so that when
a handler is already in the process of running and somehow the same or
another handler starts running -- say in a signal handler, while the
XRay handler is executing -- then we can use the same thread-local
recursion guard to stop the second handler from running.

Reviewers: kpw, eizan

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D37612

llvm-svn: 312992

1 files changed, 2 insertions, 1 deletions

diff --git a/compiler-rt/lib/xray/xray_fdr_logging_impl.h b/compiler-rt/lib/xray/xray_fdr_logging_impl.h
index ce81e4364a9..b2f7f3f239e 100644
--- a/compiler-rt/lib/xray/xray_fdr_logging_impl.h
+++ b/compiler-rt/lib/xray/xray_fdr_logging_impl.h
@@ -571,6 +571,8 @@ inline void endBufferIfFull() XRAY_NEVER_INSTRUMENT {
   }
 }
 
+thread_local volatile bool Running = false;
+
 inline void processFunctionHook(
     int32_t FuncId, XRayEntryType Entry, uint64_t TSC, unsigned char CPU,
     int (*wall_clock_reader)(clockid_t, struct timespec *),
@@ -581,7 +583,6 @@ inline void processFunctionHook(
   // don't want to be clobbering potentially partial writes already happening in
   // the thread. We use a simple thread_local latch to only allow one on-going
   // handleArg0 to happen at any given time.
-  thread_local volatile bool Running = false;
   RecursionGuard Guard{Running};
   if (!Guard) {
     assert(Running == true && "RecursionGuard is buggy!");