add workaround for kernel panics on MacOS

Author: laytan

src/threading.cpp

@@ -796,13 +796,27 @@ gb_internal void futex_wait(Futex *f, Footex val) {
 
 #elif defined(GB_SYSTEM_OSX)
 
+// IMPORTANT NOTE(laytan): We use `OS_SYNC_*_SHARED` and `UL_COMPARE_AND_WAIT_SHARED` flags here.
+// these flags tell the kernel that we are using these futexes across different processes which
+// causes it to opt-out of some optimisations.
+//
+// BUT this is not actually the case! We should be using the normal non-shared version and letting
+// the kernel optimize (I've measured it to be about 10% faster at the parsing/type checking stages).
+//
+// However we have reports of people on MacOS running into kernel panics, and this seems to fix it for them.
+// Which means there is probably a bug in the kernel in one of these non-shared optimisations causing the panic.
+//
+// The panic also doesn't seem to happen on normal M1 CPUs, and happen more on later CPUs or pro/max series.
+// Probably because they have more going on in terms of threads etc.
+
 #if __has_include(<os/os_sync_wait_on_address.h>)
 	#define DARWIN_WAIT_ON_ADDRESS_AVAILABLE
 	#include <os/os_sync_wait_on_address.h>
 #endif
 
-#define UL_COMPARE_AND_WAIT	0x00000001
-#define ULF_NO_ERRNO        0x01000000
+#define UL_COMPARE_AND_WAIT        0x00000001
+#define UL_COMPARE_AND_WAIT_SHARED 0x00000003
+#define ULF_NO_ERRNO               0x01000000
 
 extern "C" int __ulock_wait(uint32_t operation, void *addr, uint64_t value, uint32_t timeout); /* timeout is specified in microseconds */
 extern "C" int __ulock_wake(uint32_t operation, void *addr, uint64_t wake_value);
@@ -811,7 +825,7 @@ gb_internal void futex_signal(Futex *f) {
 	#ifdef DARWIN_WAIT_ON_ADDRESS_AVAILABLE
 	if (__builtin_available(macOS 14.4, *)) {
 		for (;;) {
-			int ret = os_sync_wake_by_address_any(f, sizeof(Futex), OS_SYNC_WAKE_BY_ADDRESS_NONE);
+			int ret = os_sync_wake_by_address_any(f, sizeof(Futex), OS_SYNC_WAKE_BY_ADDRESS_SHARED);
 			if (ret >= 0) {
 				return;
 			}
@@ -826,7 +840,7 @@ gb_internal void futex_signal(Futex *f) {
 	} else {
 	#endif
 	for (;;) {
-		int ret = __ulock_wake(UL_COMPARE_AND_WAIT | ULF_NO_ERRNO, f, 0);
+		int ret = __ulock_wake(UL_COMPARE_AND_WAIT_SHARED | ULF_NO_ERRNO, f, 0);
 		if (ret >= 0) {
 			return;
 		}
@@ -847,7 +861,7 @@ gb_internal void futex_broadcast(Futex *f) {
 	#ifdef DARWIN_WAIT_ON_ADDRESS_AVAILABLE
 	if (__builtin_available(macOS 14.4, *)) {
 		for (;;) {
-			int ret = os_sync_wake_by_address_all(f, sizeof(Footex), OS_SYNC_WAKE_BY_ADDRESS_NONE);
+			int ret = os_sync_wake_by_address_all(f, sizeof(Footex), OS_SYNC_WAKE_BY_ADDRESS_SHARED);
 			if (ret >= 0) {
 				return;
 			}
@@ -863,7 +877,7 @@ gb_internal void futex_broadcast(Futex *f) {
 	#endif
 	for (;;) {
 		enum { ULF_WAKE_ALL = 0x00000100 };
-		int ret = __ulock_wake(UL_COMPARE_AND_WAIT | ULF_NO_ERRNO | ULF_WAKE_ALL, f, 0);
+		int ret = __ulock_wake(UL_COMPARE_AND_WAIT_SHARED | ULF_NO_ERRNO | ULF_WAKE_ALL, f, 0);
 		if (ret == 0) {
 			return;
 		}
@@ -884,7 +898,7 @@ gb_internal void futex_wait(Futex *f, Footex val) {
 	#ifdef DARWIN_WAIT_ON_ADDRESS_AVAILABLE
 	if (__builtin_available(macOS 14.4, *)) {
 		for (;;) {
-			int ret = os_sync_wait_on_address(f, cast(uint64_t)(val), sizeof(Footex), OS_SYNC_WAIT_ON_ADDRESS_NONE);
+			int ret = os_sync_wait_on_address(f, cast(uint64_t)(val), sizeof(Footex), OS_SYNC_WAIT_ON_ADDRESS_SHARED);
 			if (ret >= 0) {
 				if (*f != val) {
 					return;
@@ -902,7 +916,7 @@ gb_internal void futex_wait(Futex *f, Footex val) {
 	} else {
 	#endif
 	for (;;) {
-		int ret = __ulock_wait(UL_COMPARE_AND_WAIT | ULF_NO_ERRNO, f, val, 0);
+		int ret = __ulock_wait(UL_COMPARE_AND_WAIT_SHARED | ULF_NO_ERRNO, f, val, 0);
 		if (ret >= 0) {
 			if (*f != val) {
 				return;