From 8c4a41f9835d56437c44631d97ef592e948385d9 Mon Sep 17 00:00:00 2001
From: Andrew Waterman <waterman@eecs.berkeley.edu>
Date: Sat, 17 Nov 2012 03:43:57 -0800
Subject: fix spinlocks; add --disable-atomics cfg opt

---
 config.h.in   |  3 +++
 configure     | 15 +++++++++++++++
 pk/atomic.h   | 49 ++++++++++++++++++++++++++++++++-----------------
 pk/frontend.c |  4 +++-
 pk/pk.ac      |  5 +++++
 5 files changed, 58 insertions(+), 18 deletions(-)

diff --git a/config.h.in b/config.h.in
index 65b5df0..b06f0a9 100644
--- a/config.h.in
+++ b/config.h.in
@@ -21,6 +21,9 @@
 /* Define if subproject MCPPBS_SPROJ_NORM is enabled */
 #undef PK_ENABLED
 
+/* Define if atomics are supported */
+#undef PK_ENABLE_ATOMICS
+
 /* Define if floating-point emulation is enabled */
 #undef PK_ENABLE_FP_EMULATION
 
diff --git a/configure b/configure
index c0def38..e9864a6 100755
--- a/configure
+++ b/configure
@@ -648,6 +648,7 @@ enable_stow
 enable_optional_subprojects
 enable_vm
 enable_fp_emulation
+enable_atomics
 '
       ac_precious_vars='build_alias
 host_alias
@@ -1283,6 +1284,7 @@ Optional Features:
                           Enable all optional subprojects
   --disable-vm            Disable virtual memory
   --disable-fp-emulation  Disable floating-point emulation
+  --disable-atomics       Emulate atomic ops nonatomically
 
 Some influential environment variables:
   CC          C compiler command
@@ -4047,6 +4049,19 @@ $as_echo "#define PK_ENABLE_FP_EMULATION /**/" >>confdefs.h
 
 fi
 
+# Check whether --enable-atomics was given.
+if test "${enable_atomics+set}" = set; then :
+  enableval=$enable_atomics;
+fi
+
+if test "x$enable_atomics" != "xno"; then :
+
+
+$as_echo "#define PK_ENABLE_ATOMICS /**/" >>confdefs.h
+
+
+fi
+
 
 
 
diff --git a/pk/atomic.h b/pk/atomic.h
index 88bb239..abd2e05 100644
--- a/pk/atomic.h
+++ b/pk/atomic.h
@@ -1,44 +1,59 @@
 #ifndef _RISCV_ATOMIC_H
 #define _RISCV_ATOMIC_H
 
-typedef struct { long val; } atomic_t;
+#include "config.h"
+
+typedef struct { volatile long val; } atomic_t;
 typedef struct { atomic_t lock; } spinlock_t;
 #define SPINLOCK_INIT {{0}}
 
-static inline long atomic_add(atomic_t* a, long inc)
+#define mb() __sync_synchronize()
+
+static inline void atomic_set(atomic_t* a, long val)
 {
-  //return __sync_fetch_and_add(&a->val, inc);
-  long ret = a->val;
-  a->val++;
-  return ret;
+  a->val = val;
 }
 
-static inline long atomic_swap(atomic_t* a, long val)
+static inline long atomic_read(atomic_t* a)
 {
-  //return __sync_lock_test_and_set(&a->val, val);
-  long reg = a->val;
-  a->val = val;
-  return reg;
+  return a->val;
 }
 
-static inline void atomic_set(atomic_t* a, long val)
+static inline long atomic_add(atomic_t* a, long inc)
 {
-  a->val = val;
+#ifdef PK_ENABLE_ATOMICS
+  return __sync_fetch_and_add(&a->val, inc);
+#else
+  long ret = atomic_read(a);
+  atomic_set(a, ret + inc);
+  return ret;
+#endif
 }
 
-static inline long atomic_read(atomic_t* a)
+static inline long atomic_swap(atomic_t* a, long val)
 {
-  return a->val;
+#ifdef PK_ENABLE_ATOMICS
+  return __sync_lock_test_and_set(&a->val, val);
+#else
+  long ret = atomic_read(a);
+  atomic_set(a, val);
+  return ret;
+#endif
 }
 
 static inline void spinlock_lock(spinlock_t* lock)
 {
-  while(atomic_read(&lock->lock))
-    while(atomic_swap(&lock->lock,-1));
+  do
+  {
+    while (atomic_read(&lock->lock))
+      ;
+  } while (atomic_swap(&lock->lock, -1));
+  mb();
 }
 
 static inline void spinlock_unlock(spinlock_t* lock)
 {
+  mb();
   atomic_set(&lock->lock,0);
 }
 
diff --git a/pk/frontend.c b/pk/frontend.c
index 4e4c138..1818b0f 100644
--- a/pk/frontend.c
+++ b/pk/frontend.c
@@ -17,11 +17,13 @@ sysret_t frontend_syscall(long n, long a0, long a1, long a2, long a3)
   magic_mem[3] = a2;
   magic_mem[4] = a3;
 
-  asm volatile ("cflush; fence");
+  mb();
 
   mtpcr(PCR_TOHOST, magic_mem);
   while (mtpcr(PCR_FROMHOST, 0) == 0);
 
+  mb();
+
   sysret_t ret = {magic_mem[0],magic_mem[1]};
 
   spinlock_unlock(&lock);
diff --git a/pk/pk.ac b/pk/pk.ac
index 47c9207..fdcaa65 100644
--- a/pk/pk.ac
+++ b/pk/pk.ac
@@ -7,3 +7,8 @@ AC_ARG_ENABLE([fp-emulation], AS_HELP_STRING([--disable-fp-emulation], [Disable
 AS_IF([test "x$enable_fp_emulation" != "xno"], [
   AC_DEFINE([PK_ENABLE_FP_EMULATION],,[Define if floating-point emulation is enabled])
 ])
+
+AC_ARG_ENABLE([atomics], AS_HELP_STRING([--disable-atomics], [Emulate atomic ops nonatomically]))
+AS_IF([test "x$enable_atomics" != "xno"], [
+  AC_DEFINE([PK_ENABLE_ATOMICS],,[Define if atomics are supported])
+])
-- 
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