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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
This commit is contained in:
Dmitry Vyukov 2014-12-25 10:32:25 +00:00
parent 25b383ac66
commit bda655004e
1 changed files with 5 additions and 7 deletions
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12
compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cc
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@ -111,15 +111,13 @@ void ThreadContext::OnStarted(void *arg) {
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 "