futex text: avoid spurious non-atomic reads

Author: RalfJung

tests/pass-dep/concurrency/linux-futex.rs

@@ -2,7 +2,7 @@
 //@compile-flags: -Zmiri-disable-isolation
 
 use std::mem::MaybeUninit;
-use std::ptr;
+use std::ptr::{self, addr_of};
 use std::sync::atomic::AtomicI32;
 use std::sync::atomic::Ordering;
 use std::thread;
@@ -13,15 +13,15 @@ fn wake_nobody() {
 
     // Wake 1 waiter. Expect zero waiters woken up, as nobody is waiting.
     unsafe {
-        assert_eq!(libc::syscall(libc::SYS_futex, &futex as *const i32, libc::FUTEX_WAKE, 1), 0);
+        assert_eq!(libc::syscall(libc::SYS_futex, addr_of!(futex), libc::FUTEX_WAKE, 1), 0);
     }
 
     // Same, but without omitting the unused arguments.
     unsafe {
         assert_eq!(
             libc::syscall(
                 libc::SYS_futex,
-                &futex as *const i32,
+                addr_of!(futex),
                 libc::FUTEX_WAKE,
                 1,
                 ptr::null::<libc::timespec>(),
@@ -52,7 +52,7 @@ fn wait_wrong_val() {
         assert_eq!(
             libc::syscall(
                 libc::SYS_futex,
-                &futex as *const i32,
+                addr_of!(futex),
                 libc::FUTEX_WAIT,
                 456,
                 ptr::null::<libc::timespec>(),
@@ -73,7 +73,7 @@ fn wait_timeout() {
         assert_eq!(
             libc::syscall(
                 libc::SYS_futex,
-                &futex as *const i32,
+                addr_of!(futex),
                 libc::FUTEX_WAIT,
                 123,
                 &libc::timespec { tv_sec: 0, tv_nsec: 200_000_000 },
@@ -110,7 +110,7 @@ fn wait_absolute_timeout() {
         assert_eq!(
             libc::syscall(
                 libc::SYS_futex,
-                &futex as *const i32,
+                addr_of!(futex),
                 libc::FUTEX_WAIT_BITSET,
                 123,
                 &timeout,
@@ -136,7 +136,7 @@ fn wait_wake() {
             assert_eq!(
                 libc::syscall(
                     libc::SYS_futex,
-                    &FUTEX as *const i32,
+                    addr_of!(FUTEX),
                     libc::FUTEX_WAKE,
                     10, // Wake up at most 10 threads.
                 ),
@@ -149,7 +149,7 @@ fn wait_wake() {
         assert_eq!(
             libc::syscall(
                 libc::SYS_futex,
-                &FUTEX as *const i32,
+                addr_of!(FUTEX),
                 libc::FUTEX_WAIT,
                 0,
                 ptr::null::<libc::timespec>(),
@@ -173,7 +173,7 @@ fn wait_wake_bitset() {
             assert_eq!(
                 libc::syscall(
                     libc::SYS_futex,
-                    &FUTEX as *const i32,
+                    addr_of!(FUTEX),
                     libc::FUTEX_WAKE_BITSET,
                     10, // Wake up at most 10 threads.
                     ptr::null::<libc::timespec>(),
@@ -188,7 +188,7 @@ fn wait_wake_bitset() {
             assert_eq!(
                 libc::syscall(
                     libc::SYS_futex,
-                    &FUTEX as *const i32,
+                    addr_of!(FUTEX),
                     libc::FUTEX_WAKE_BITSET,
                     10, // Wake up at most 10 threads.
                     ptr::null::<libc::timespec>(),
@@ -204,7 +204,7 @@ fn wait_wake_bitset() {
         assert_eq!(
             libc::syscall(
                 libc::SYS_futex,
-                &FUTEX as *const i32,
+                addr_of!(FUTEX),
                 libc::FUTEX_WAIT_BITSET,
                 0,
                 ptr::null::<libc::timespec>(),
@@ -244,7 +244,7 @@ fn concurrent_wait_wake() {
             unsafe {
                 let ret = libc::syscall(
                     libc::SYS_futex,
-                    &FUTEX as *const AtomicI32,
+                    addr_of!(FUTEX),
                     libc::FUTEX_WAIT,
                     HELD,
                     ptr::null::<libc::timespec>(),
@@ -267,7 +267,7 @@ fn concurrent_wait_wake() {
         FUTEX.store(FREE, Ordering::Relaxed);
         unsafe {
             DATA = 1;
-            libc::syscall(libc::SYS_futex, &FUTEX as *const AtomicI32, libc::FUTEX_WAKE, 1);
+            libc::syscall(libc::SYS_futex, addr_of!(FUTEX), libc::FUTEX_WAKE, 1);
         }
 
         t.join().unwrap();