From 8ce03686edafbbdae47e7f451211c53542f6649b Mon Sep 17 00:00:00 2001
From: John Sully <john@csquare.ca>
Date: Wed, 27 Jan 2021 05:05:05 +0000
Subject: [PATCH] Ensure the C lock implementation behaves the same as the ASM

Former-commit-id: b5ddc11c46d2eabd28fae4c69927c356dd18bf6e
---
 src/fastlock.cpp | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/src/fastlock.cpp b/src/fastlock.cpp
index 8c1c5f6e4..6e6b6e4d2 100644
--- a/src/fastlock.cpp
+++ b/src/fastlock.cpp
@@ -356,26 +356,32 @@ extern "C" void fastlock_lock(struct fastlock *lock, spin_worker worker)
     __atomic_load(&g_fHighCpuPressure, &fHighPressure, __ATOMIC_RELAXED);
     unsigned loopLimit = fHighPressure ? 0x10000 : 0x100000;
 
-    // WARNING:::: THIS DOESN"T MATCH ASM
-    for (;;)
-    {
-        __atomic_load(&lock->m_ticket.u, &ticketT.u, __ATOMIC_ACQUIRE);
-        if ((ticketT.u & 0xffff) == myticket)
-            break;
+    if (worker != nullptr) {
+        for (;;) {
+            __atomic_load(&lock->m_ticket.u, &ticketT.u, __ATOMIC_ACQUIRE);
+            if ((ticketT.u & 0xffff) == myticket)
+                break;
+            if (!worker())
+                goto LNormalLoop;
+        }
+    } else {
+LNormalLoop:
+        for (;;)
+        {
+            __atomic_load(&lock->m_ticket.u, &ticketT.u, __ATOMIC_ACQUIRE);
+            if ((ticketT.u & 0xffff) == myticket)
+                break;
 
-        if (worker != nullptr) {
-            worker();
-        } else {
 #if defined(__i386__) || defined(__amd64__)
             __asm__ __volatile__ ("pause");
 #elif defined(__aarch64__)
             __asm__ __volatile__ ("yield");
 #endif
-        }
 
-        if ((++cloops % loopLimit) == 0)
-        {
-            fastlock_sleep(lock, tid, ticketT.u, myticket);
+            if ((++cloops % loopLimit) == 0)
+            {
+                fastlock_sleep(lock, tid, ticketT.u, myticket);
+            }
         }
     }