From 94ed1c637c839dbcb06df6e83c0c8416bad15674 Mon Sep 17 00:00:00 2001
From: Bartosz Taudul <wolf.pld@gmail.com>
Date: Thu, 21 Mar 2019 21:59:51 +0100
Subject: [PATCH] Try to check if cntcvt reads are monotonic.

https://lore.kernel.org/patchwork/patch/904607/
---
 client/TracyProfiler.cpp | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/client/TracyProfiler.cpp b/client/TracyProfiler.cpp
index 3971b1f4..20d4f0b0 100644
--- a/client/TracyProfiler.cpp
+++ b/client/TracyProfiler.cpp
@@ -203,6 +203,26 @@ static int64_t SetupHwTimer()
 
     sigaction( SIGILL, &oldact, nullptr );
     GetTimeImpl = GetTimeImplCntvct;
+
+    // Check if cntcvt is monotonic (there is faulty hw out there)
+    enum { NumProbes = 32 * 1024 };
+    int64_t probe[NumProbes];
+    for( int j=0; j<10; j++ )
+    {
+        for( int i=0; i<NumProbes; i++ )
+        {
+            probe[i] = Profiler::GetTime();
+        }
+        for( int i=1; i<NumProbes; i++ )
+        {
+            if( probe[i] < probe[i-1] )
+            {
+                GetTimeImpl = GetTimeImplFallback;
+                return Profiler::GetTime();
+            }
+        }
+    }
+
     return Profiler::GetTime();
 }
 #else