tsan: fix trace initialization during thread id reuse
The current code leaves the first event in the trace part uninitialized
(from the previous thread). It can cause unpredictable behavior
during stack/mutexset restoration.
Initialize the first event to a fake harmless memory access.
llvm-svn: 224834
diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cc b/compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cc
index d84cd44..065ba88 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cc
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cc
@@ -111,15 +111,13 @@
thr->dd_pt = ctx->dd->CreatePhysicalThread();
thr->dd_lt = ctx->dd->CreateLogicalThread(unique_id);
}
+ thr->fast_state.SetHistorySize(flags()->history_size);
+ // Commit switch to the new part of the trace.
+ // TraceAddEvent will reset stack0/mset0 in the new part for us.
+ TraceAddEvent(thr, thr->fast_state, EventTypeMop, 0);
+
thr->fast_synch_epoch = epoch0;
AcquireImpl(thr, 0, &sync);
- thr->fast_state.SetHistorySize(flags()->history_size);
- const uptr trace = (epoch0 / kTracePartSize) % TraceParts();
- Trace *thr_trace = ThreadTrace(thr->tid);
- TraceHeader *hdr = &thr_trace->headers[trace];
- hdr->epoch0 = epoch0;
- ObtainCurrentStack(thr, 0, &hdr->stack0);
- hdr->mset0 = thr->mset;
StatInc(thr, StatSyncAcquire);
sync.Reset(&thr->clock_cache);
DPrintf("#%d: ThreadStart epoch=%zu stk_addr=%zx stk_size=%zx "