gem5: one concrete minimal example of a coherentxbar snoop

userland/c/atomic.c

@@ -4,9 +4,9 @@
 #include <assert.h>
 #include <stdatomic.h>
 #include <stdio.h>
-#include <threads.h>
-#include <string.h>
 #include <stdlib.h>
+#include <string.h>
+#include <threads.h>
 
 atomic_int acnt;
 int cnt;

userland/c/atomic/README.adoc

@@ -0,0 +1 @@
+https://cirosantilli.com/linux-kernel-module-cheat#atomic-c

userland/c/atomic/aarch64_add.c

@@ -0,0 +1,2 @@
+#define LKMC_USERLAND_ATOMIC_AARCH64_ADD 1
+#include "main.h"

userland/c/atomic/aarch64_ldadd.c

@@ -0,0 +1,2 @@
+#define LKMC_USERLAND_ATOMIC_AARCH64_LDADD 1
+#include "main.h"

userland/c/atomic/aarch64_ldaxr_stlxr.c

@@ -0,0 +1,2 @@
+#define LKMC_USERLAND_ATOMIC_LDAXR_STLXR 1
+#include "main.h"

userland/c/atomic/build

@@ -0,0 +1 @@
+../build

userland/c/atomic/fail.c

@@ -0,0 +1,2 @@
+#define LKMC_USERLAND_ATOMIC_FAIL 1
+#include "main.h"

userland/c/atomic/main.h

@@ -0,0 +1,118 @@
+// https://cirosantilli.com/linux-kernel-module-cheat#atomic-c */
+
+#if __STDC_VERSION__ >= 201112L && !defined(__STDC_NO_THREADS__)
+#include <assert.h>
+#include <stdatomic.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <threads.h>
+
+#if LKMC_USERLAND_ATOMIC_STD_ATOMIC
+atomic_uint global = 0;
+#else
+uint64_t global = 0;
+#endif
+
+int my_thread_main(void *thr_data) {
+    size_t niters = *(size_t *)thr_data;
+    for (size_t i = 0; i < niters; ++i) {
+#if LKMC_USERLAND_ATOMIC_X86_64_INC
+        __asm__ __volatile__ (
+            "incq %0;"
+            : "+g" (global),
+              "+g" (i)
+            :
+            :
+        );
+#elif LKMC_USERLAND_ATOMIC_X86_64_LOCK_INC
+        __asm__ __volatile__ (
+            "lock incq %0;"
+            : "+m" (global),
+              "+g" (i)
+            :
+            :
+        );
+#elif LKMC_USERLAND_ATOMIC_AARCH64_ADD
+        __asm__ __volatile__ (
+            "add %0, %0, 1;"
+            : "+r" (global),
+              "+g" (i)
+            :
+            :
+        );
+#elif LKMC_USERLAND_ATOMIC_LDAXR_STLXR
+        uint64_t scratch64;
+        uint64_t scratch32;
+        __asm__ __volatile__ (
+            "1:"
+            "ldaxr %[scratch64], [%[addr]];"
+            "add   %[scratch64], %[scratch64], 1;"
+            "stlxr %w[scratch32], %[scratch64], [%[addr]];"
+            "cbnz  %w[scratch32], 1b;"
+            : "=m" (global),
+              "+g" (i),
+              [scratch64] "=&r" (scratch64),
+              [scratch32] "=&r" (scratch32)
+            : [addr] "r" (&global)
+            :
+        );
+#elif LKMC_USERLAND_ATOMIC_AARCH64_LDADD
+        __asm__ __volatile__ (
+            "ldadd %[inc], xzr, [%[addr]];"
+            : "=m" (global),
+              "+g" (i)
+            : [inc] "r" (1),
+              [addr] "r" (&global)
+            :
+        );
+#else
+        __asm__ __volatile__ (
+            ""
+            : "+g" (i)
+            : "g" (global)
+            :
+        );
+        global++;
+#endif
+    }
+    return 0;
+}
+#endif
+
+int main(int argc, char **argv) {
+#if __STDC_VERSION__ >= 201112L && !defined(__STDC_NO_THREADS__)
+    size_t niters, nthreads;
+    thrd_t *threads;
+    if (argc > 1) {
+        nthreads = strtoull(argv[1], NULL, 0);
+    } else {
+        nthreads = 2;
+    }
+    if (argc > 2) {
+        niters = strtoull(argv[2], NULL, 0);
+    } else {
+        niters = 10;
+    }
+    threads = malloc(sizeof(thrd_t) * nthreads);
+    for(size_t i = 0; i < nthreads; ++i)
+        assert(thrd_create(threads + i, my_thread_main, &niters) == thrd_success);
+    for(size_t i = 0; i < nthreads; ++i)
+        assert(thrd_join(threads[i], NULL) == thrd_success);
+    free(threads);
+    uint64_t expect = nthreads * niters;
+#if LKMC_USERLAND_ATOMIC_FAIL || \
+    LKMC_USERLAND_ATOMIC_X86_64_INC || \
+    LKMC_USERLAND_ATOMIC_AARCH64_ADD
+    printf("expect %ju\n", (uintmax_t)expect);
+    printf("global %ju\n", (uintmax_t)global);
+#else
+    assert(global == expect);
+#endif
+#else
+    (void)argc;
+    (void)argv;
+#endif
+}
+

userland/c/atomic/mutex.c

@@ -0,0 +1,2 @@
+#define LKMC_USERLAND_ATOMIC_MUTEX 1
+#include "main.h"

userland/c/atomic/std_atomic.c

@@ -0,0 +1,2 @@
+#define LKMC_USERLAND_ATOMIC_STD_ATOMIC 1
+#include "main.h"

userland/c/atomic/test

@@ -0,0 +1 @@
+../test

userland/c/atomic/x86_64_inc.c

@@ -0,0 +1,2 @@
+#define LKMC_USERLAND_ATOMIC_X86_64_INC 1
+#include "main.h"

userland/c/atomic/x86_64_lock_inc.c

@@ -0,0 +1,2 @@
+#define LKMC_USERLAND_ATOMIC_X86_64_LOCK_INC 1
+#include "main.h"

userland/cpp/atomic/README.adoc

@@ -1 +1 @@
-// https://cirosantilli.com/linux-kernel-module-cheat#atomic-cpp
+https://cirosantilli.com/linux-kernel-module-cheat#atomic-cpp