From 84d47c358b1d07b9155474d7075e082c52147ebc Mon Sep 17 00:00:00 2001
From: Richard Braun <rbraun@sceen.net>
Date: Fri, 16 Aug 2019 20:02:37 +0200
Subject: Replace some barrier()s with local atomic fences

---
 kern/thread.c |  4 +++-
 kern/thread.h | 13 +++++++------
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/kern/thread.c b/kern/thread.c
index 71943c04..0bad0752 100644
--- a/kern/thread.c
+++ b/kern/thread.c
@@ -96,6 +96,7 @@
 #include <kern/cpumap.h>
 #include <kern/init.h>
 #include <kern/kmem.h>
+#include <kern/latomic.h>
 #include <kern/list.h>
 #include <kern/macros.h>
 #include <kern/panic.h>
@@ -674,7 +675,9 @@ thread_runq_schedule(struct thread_runq *runq)
          * and locking the run queue again is equivalent to a full memory
          * barrier.
          */
+        latomic_fence(LATOMIC_ACQ_REL);
         tcb_switch(&prev->tcb, &next->tcb);
+        latomic_fence(LATOMIC_ACQ_REL);
 
         /*
          * The thread is dispatched on a processor once again.
@@ -685,7 +688,6 @@ thread_runq_schedule(struct thread_runq *runq)
          *    referenced any more.
          *  - The current thread may have been migrated to another processor.
          */
-        barrier();
         thread_runq_schedule_load(prev);
 
         next = NULL;
diff --git a/kern/thread.h b/kern/thread.h
index 0c8c1014..d77b35f3 100644
--- a/kern/thread.h
+++ b/kern/thread.h
@@ -43,6 +43,7 @@
 #include <kern/init.h>
 #include <kern/cpumap.h>
 #include <kern/kernel.h>
+#include <kern/latomic.h>
 #include <kern/macros.h>
 #include <kern/spinlock_types.h>
 #include <kern/turnstile_types.h>
@@ -548,7 +549,7 @@ thread_pin(void)
     thread = thread_self();
     thread->pin_level++;
     assert(thread->pin_level != 0);
-    barrier();
+    latomic_fence(LATOMIC_ACQ_REL);
 }
 
 /*
@@ -561,7 +562,7 @@ thread_unpin(void)
 {
     struct thread *thread;
 
-    barrier();
+    latomic_fence(LATOMIC_ACQ_REL);
     thread = thread_self();
     assert(thread->pin_level != 0);
     thread->pin_level--;
@@ -595,7 +596,7 @@ thread_preempt_disable(void)
     thread = thread_self();
     thread->preempt_level++;
     assert(thread->preempt_level != 0);
-    barrier();
+    latomic_fence(LATOMIC_ACQ_REL);
 }
 
 /*
@@ -613,7 +614,7 @@ thread_preempt_enable_no_resched(void)
 {
     struct thread *thread;
 
-    barrier();
+    latomic_fence(LATOMIC_ACQ_REL);
     thread = thread_self();
     assert(thread->preempt_level != 0);
     thread->preempt_level--;
@@ -713,7 +714,7 @@ thread_intr_enter(void)
 
     thread->intr_level++;
     assert(thread->intr_level != 0);
-    barrier();
+    latomic_fence(LATOMIC_ACQ_REL);
 }
 
 /*
@@ -726,7 +727,7 @@ thread_intr_leave(void)
 {
     struct thread *thread;
 
-    barrier();
+    latomic_fence(LATOMIC_ACQ_REL);
     thread = thread_self();
     assert(thread->intr_level != 0);
     thread->intr_level--;
-- 
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