diff --git a/compiler-rt/lib/msan/msan_interceptors.cpp b/compiler-rt/lib/msan/msan_interceptors.cpp
--- a/compiler-rt/lib/msan/msan_interceptors.cpp
+++ b/compiler-rt/lib/msan/msan_interceptors.cpp
@@ -1034,6 +1034,7 @@
   MsanThread *t = (MsanThread *)arg;
   SetCurrentThread(t);
   t->Init();
+  SetSigProcMask(&t->starting_sigset_, nullptr);
   return t->ThreadStart();
 }
 
@@ -1049,7 +1050,7 @@
   AdjustStackSize(attr);
 
   MsanThread *t = MsanThread::Create(callback, param);
-
+  ScopedBlockSignals block(&t->starting_sigset_);
   int res = REAL(pthread_create)(th, attr, MsanThreadStartFunc, t);
 
   if (attr == &myattr)
diff --git a/compiler-rt/lib/msan/msan_thread.h b/compiler-rt/lib/msan/msan_thread.h
--- a/compiler-rt/lib/msan/msan_thread.h
+++ b/compiler-rt/lib/msan/msan_thread.h
@@ -15,7 +15,7 @@
 
 #include "msan_allocator.h"
 #include "sanitizer_common/sanitizer_common.h"
-
+#include "sanitizer_common/sanitizer_posix.h"
 namespace __msan {
 
 class MsanThread {
@@ -45,6 +45,7 @@
   MsanThreadLocalMallocStorage &malloc_storage() { return malloc_storage_; }
 
   int destructor_iterations_;
+  __sanitizer_sigset_t starting_sigset_;
 
  private:
   // NOTE: There is no MsanThread constructor. It is allocated