[PATCH v2 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

[Jeff Fan <jeff.fan@intel.com>]

The GCC 5.4 will optimize mNumberToFinish in EarlyInitializeCpu(). It will cause
S3 resume failure.

Adding *volatile* could make sure compiler does not so such optimization.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
index 3fb6864..6324d7e 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
@@ -55,7 +55,7 @@ AsmGetAddressMap (
 #define LEGACY_REGION_BASE    (0xA0000 - LEGACY_REGION_SIZE)
 
 ACPI_CPU_DATA                mAcpiCpuData;
-UINT32                       mNumberToFinish;
+volatile UINT32              mNumberToFinish;
 MP_CPU_EXCHANGE_INFO         *mExchangeInfo;
 BOOLEAN                      mRestoreSmmConfigurationInS3 = FALSE;
 VOID                         *mGdtForAp = NULL;
@@ -371,7 +371,7 @@ EarlyMPRendezvousProcedure (
   //
   // Count down the number with lock mechanism.
   //
-  InterlockedDecrement (&mNumberToFinish);
+  InterlockedDecrement ((UINT32 *) &mNumberToFinish);
 }
 
 /**
-- 
2.9.3.windows.2