contrib: universal atomic operations

6 files changed, 164 insertions, 0 deletions

diff --git a/Knot.files b/Knot.files
index f394d0eac..d4afe2399 100644
--- a/Knot.files
+++ b/Knot.files
@@ -1,4 +1,5 @@
 src/contrib/asan.h
+src/contrib/atomic.h
 src/contrib/base32hex.c
 src/contrib/base32hex.h
 src/contrib/base64.c
@@ -620,6 +621,7 @@ tests-fuzz/knotd_wrap/server.c
 tests-fuzz/knotd_wrap/tcp-handler.c
 tests-fuzz/knotd_wrap/udp-handler.c
 tests-fuzz/main.c
+tests/contrib/test_atomic.c
 tests/contrib/test_base32hex.c
 tests/contrib/test_base64.c
 tests/contrib/test_base64url.c
diff --git a/src/contrib/Makefile.inc b/src/contrib/Makefile.inc
index d35c7d204..09ecdde90 100644
--- a/src/contrib/Makefile.inc
+++ b/src/contrib/Makefile.inc
@@ -24,6 +24,7 @@ EXTRA_DIST += \
 
 libcontrib_la_SOURCES = \
 	contrib/asan.h				\
+	contrib/atomic.h			\
 	contrib/base32hex.c			\
 	contrib/base32hex.h			\
 	contrib/base64.c			\
diff --git a/src/contrib/atomic.h b/src/contrib/atomic.h
new file mode 100644
index 000000000..adc2d5a46
--- /dev/null
+++ b/src/contrib/atomic.h
@@ -0,0 +1,64 @@
+/*  Copyright (C) 2023 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/*!
+ * \brief C11 atomic operations with fallbacks.
+ */
+
+#pragma once
+
+#if (__STDC_VERSION__ >= 201112L) && !defined(__STDC_NO_ATOMICS__)
+ #define KNOT_HAVE_ATOMIC            /* C11 */
+
+ #include <stdatomic.h>
+
+ #define ATOMIC_SET(dst, val) atomic_store_explicit(&(dst), (val), memory_order_relaxed)
+ #define ATOMIC_GET(src)      atomic_load_explicit(&(src), memory_order_relaxed)
+ #define ATOMIC_ADD(dst, val) (void)atomic_fetch_add_explicit(&(dst), (val), memory_order_relaxed)
+ #define ATOMIC_SUB(dst, val) (void)atomic_fetch_sub_explicit(&(dst), (val), memory_order_relaxed)
+
+ typedef atomic_uint_fast64_t knot_atomic_uint64_t;
+#elif defined(HAVE_ATOMIC)           /* GCC */
+ #define KNOT_HAVE_ATOMIC
+
+ #include <stdint.h>
+
+ #define ATOMIC_SET(dst, val) __atomic_store_n(&(dst), (val), __ATOMIC_RELAXED)
+ #define ATOMIC_GET(src)      __atomic_load_n(&(src), __ATOMIC_RELAXED)
+ #define ATOMIC_ADD(dst, val) __atomic_add_fetch(&(dst), (val), __ATOMIC_RELAXED)
+ #define ATOMIC_SUB(dst, val) __atomic_sub_fetch(&(dst), (val), __ATOMIC_RELAXED)
+
+ typedef uint64_t knot_atomic_uint64_t;
+#elif defined(HAVE_SYNC_ATOMIC)      /* obsolete GCC, partial support only. */
+ #warning "Full atomic operations not availabe, using partially unreliable replacement."
+ #define ATOMIC_SET(dst, val) ((dst) = (val))
+ #define ATOMIC_GET(src)      __sync_fetch_and_or(&(src), 0)
+ #define ATOMIC_ADD(dst, val) __sync_add_and_fetch(&(dst), (val))
+ #define ATOMIC_SUB(dst, val) __sync_sub_and_fetch(&(dst), (val))
+
+ typedef uint64_t knot_atomic_uint64_t;
+#else                                /* Fallback, non-atomic. */
+ #warning "Atomic operations not availabe, using unreliable replacement."
+
+ #include <stdint.h>
+
+ #define ATOMIC_SET(dst, val) ((dst) = (val))
+ #define ATOMIC_GET(src)      (src)
+ #define ATOMIC_ADD(dst, val) ((dst) += (val))
+ #define ATOMIC_SUB(dst, val) ((dst) -= (val))
+
+ typedef uint64_t knot_atomic_uint64_t;
+#endif
diff --git a/tests/.gitignore b/tests/.gitignore
index e6b410cc5..a9763744b 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -1,6 +1,7 @@
 /tap/runtests
 /runtests.log
 
+/contrib/test_atomic
 /contrib/test_base32hex
 /contrib/test_base64
 /contrib/test_base64url
diff --git a/tests/Makefile.am b/tests/Makefile.am
index eb6f1aa85..83966a4bf 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -48,6 +48,7 @@ libtap_la_SOURCES = \
 EXTRA_PROGRAMS = tap/runtests
 
 check_PROGRAMS = \
+	contrib/test_atomic			\
 	contrib/test_base32hex			\
 	contrib/test_base64			\
 	contrib/test_base64url			\
diff --git a/tests/contrib/test_atomic.c b/tests/contrib/test_atomic.c
new file mode 100644
index 000000000..2956c7a6e
--- /dev/null
+++ b/tests/contrib/test_atomic.c
@@ -0,0 +1,95 @@
+/*  Copyright (C) 2023 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <signal.h>
+#include <tap/basic.h>
+
+#include "contrib/atomic.h"
+#include "knot/server/dthreads.h"
+
+#define THREADS 16
+#define CYCLES1 100000
+#define CYCLES2 2000000
+#define UPPER 0xffffffff00000000
+#define LOWER 0x00000000ffffffff
+
+static volatile knot_atomic_uint64_t counter_add = 0;
+static volatile knot_atomic_uint64_t counter_sub = 0;
+static volatile knot_atomic_uint64_t atomic_var;
+static int errors_set_get = 0;
+
+static int thread_add(struct dthread *thread)
+{
+	for (int i = 0; i < CYCLES1; i++) {
+		ATOMIC_ADD(counter_add, 7);
+		ATOMIC_SUB(counter_sub, 7);
+	}
+
+	return 0;
+}
+
+static int thread_set(struct dthread *thread)
+{
+	u_int64_t val = (dt_get_id(thread) % 2) ? UPPER : LOWER;
+
+	for (int i = 0; i < CYCLES2; i++) {
+		ATOMIC_SET(atomic_var, val);
+		volatile u_int64_t read = ATOMIC_GET(atomic_var);
+		if (read != UPPER && read != LOWER) {
+			// Non-atomic counter, won't be accurate!
+			// However, it's sufficient for fault detection.
+			errors_set_get++;
+		}
+	}
+
+	return 0;
+}
+
+// Signal handler
+static void interrupt_handle(int s)
+{
+}
+
+int main(int argc, char *argv[])
+{
+	plan_lazy();
+
+	// Register service and signal handler
+	struct sigaction sa;
+	sa.sa_handler = interrupt_handle;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = 0;
+	sigaction(SIGALRM, &sa, NULL); // Interrupt
+
+	// Test for atomicity of ATOMIC_ADD and ATOMIC_SUB.
+	dt_unit_t *unit = dt_create(THREADS, thread_add, NULL, NULL);
+	dt_start(unit);
+	dt_join(unit);
+	dt_delete(&unit);
+
+	is_int(THREADS * CYCLES1 * 7,  counter_add, "atomicity of ATOMIC_ADD");
+	is_int(THREADS * CYCLES1 * 7, -counter_sub, "atomicity of ATOMIC_SUB");
+
+	// Test for atomicity of ATOMIC_SET and ATOMIC_GET.
+	unit = dt_create(THREADS, thread_set, NULL, NULL);
+	dt_start(unit);
+	dt_join(unit);
+	dt_delete(&unit);
+
+	is_int(0, errors_set_get, "atomicity of ATOMIC_SET / ATOMIC_GET");
+
+	return 0;
+}