ColinIanKing
commented
1 year ago Please try the following patch:
diff --git a/stress-peterson.c b/stress-peterson.c
index 0ef8b430..7fcd01aa 100644
--- a/stress-peterson.c
+++ b/stress-peterson.c
@@ -17,6 +17,7 @@
*
*/
#include "stress-ng.h"
+#include "core-arch.h"
#include "core-cpu-cache.h"
static const stress_help_t help[] = {
@@ -25,7 +26,63 @@ static const stress_help_t help[] = {
{ NULL, NULL, NULL }
};
-#if defined(HAVE_SHIM_MFENCE)
+#if defined(STRESS_ARCH_X86)
+
+#define HAVE_PETERSON_SET_GET
+
+static inline ALWAYS_INLINE void set_bool(volatile bool *ptr, const bool value)
+{
+ *ptr = value;
+}
+
+static inline ALWAYS_INLINE void set_int(volatile int *ptr, const int value)
+{
+ *ptr = value;
+}
+
+static inline ALWAYS_INLINE bool get_bool(volatile bool *ptr)
+{
+ return *ptr;
+}
+
+static inline ALWAYS_INLINE bool get_int(volatile int *ptr)
+{
+ return *ptr;
+}
+#elif defined(HAVE_ATOMIC_LOAD) && \
+ defined(HAVE_ATOMIC_STORE)
+
+#define HAVE_PETERSON_SET_GET
+
+static inline ALWAYS_INLINE void set_bool(volatile bool *ptr, const bool value)
+{
+ __atomic_store(ptr, &value, __ATOMIC_RELAXED);
+}
+
+static inline ALWAYS_INLINE void set_int(volatile int *ptr, const int value)
+{
+ __atomic_store(ptr, &value, __ATOMIC_RELAXED);
+}
+
+static inline ALWAYS_INLINE bool get_bool(volatile bool *ptr)
+{
+ bool value;
+
+ __atomic_load(ptr, &value, __ATOMIC_RELAXED);
+ return value;
+}
+
+static inline ALWAYS_INLINE int get_int(volatile int *ptr)
+{
+ int value;
+
+ __atomic_load(ptr, &value, __ATOMIC_RELAXED);
+ return value;
+}
+#endif
+
+#if defined(HAVE_SHIM_MFENCE) && \
+ defined(HAVE_PETERSON_SET_GET)
typedef struct {
volatile int turn;
@@ -53,10 +110,12 @@ static void stress_peterson_p0(const stress_args_t *args)
double t;
t = stress_time_now();
- peterson->m.flag[0] = true;
- peterson->m.turn = 1;
+ set_bool(&peterson->m.flag[0], true);
+ shim_mb();
+ set_int(&peterson->m.turn, 1);
+ shim_mb();
shim_mfence();
- while (peterson->m.flag[1] && (peterson->m.turn == 1)) {
+ while (get_bool(&peterson->m.flag[1]) && (get_int(&peterson->m.turn) == 1)) {
}
/* Critical section */
@@ -64,7 +123,9 @@ static void stress_peterson_p0(const stress_args_t *args)
peterson->m.check++;
check1 = peterson->m.check;
- peterson->m.flag[0] = false;
+ shim_mb();
+ set_bool(&peterson->m.flag[0], false);
+ shim_mb();
shim_mfence();
peterson->p0.duration += stress_time_now() - t;
peterson->p0.count += 1.0;
@@ -81,8 +142,10 @@ static void stress_peterson_p1(const stress_args_t *args)
double t;
t = stress_time_now();
- peterson->m.flag[1] = true;
- peterson->m.turn = 0;
+ set_bool(&peterson->m.flag[1], true);
+ shim_mb();
+ set_int(&peterson->m.turn, 0);
+ shim_mb();
shim_mfence();
while (peterson->m.flag[0] && (peterson->m.turn == 0)) {
}
@@ -93,7 +156,9 @@ static void stress_peterson_p1(const stress_args_t *args)
check1 = peterson->m.check;
inc_counter(args);
- peterson->m.flag[1] = false;
+ shim_mb();
+ set_bool(&peterson->m.flag[1], false);
+ shim_mb();
shim_mfence();
peterson->p1.duration += stress_time_now() - t;
peterson->p1.count += 1.0;
woodrow-shen
On riscv smp hardware, we found that peterson stressor failed the check from time to time as below: Stress-ng version: 0.15.06 Hardware: riscv 2 cores How to reproduce it:
stress-ng --peterson 2 --verboseAfter some surveys, I get some discussion that peterson algorithm may not work on multi-cores system[1] due to memory ordering and architecture specific. For example, [2] shares the point:
Besides, [3] and [4] mention about atomic operations should be used for lock / unlocking, and maybe it's worth to try. I'm not sure what other arches are like, so I'm asking here to raise the concern and looking for help, if we can get more data or start to improve this case.
Thanks,
[1] https://www.scaler.com/topics/petersons-solution/ [2] https://w3.cs.jmu.edu/kirkpams/OpenCSF/Books/csf/html/CritSect.html [3] https://www.cs.uic.edu/~jbell/CourseNotes/OperatingSystems/5_Synchronization.html [4] https://stackoverflow.com/questions/11588514/a-tested-implementation-of-peterson-lock-algorithm [5] https://www.eecs.yorku.ca/course_archive/2020-21/S/3221/Lect6.pdf [6] https://web.cecs.pdx.edu/~harry/riscv/RISCV-Summary.pdf