don't talk about 'Data race' when both accesses are atomic

Author: RalfJung

src/tools/miri/src/concurrency/data_race.rs

@@ -845,6 +845,7 @@ impl VClockAlloc {
     ) -> InterpResult<'tcx> {
         let (current_index, current_clocks) = global.current_thread_state(thread_mgr);
         let mut action = Cow::Borrowed(action);
+        let mut involves_non_atomic = true;
         let write_clock;
         #[rustfmt::skip]
         let (other_action, other_thread, other_clock) =
@@ -856,6 +857,7 @@ impl VClockAlloc {
             } else if is_atomic && let Some(atomic) = mem_clocks.atomic() && atomic.size != access_size {
                 // This is only a race if we are not synchronized with all atomic accesses, so find
                 // the one we are not synchronized with.
+                involves_non_atomic = false;
                 action = format!("{}-byte (different-size) {action}", access_size.bytes()).into();
                 if let Some(idx) = Self::find_gt_index(&atomic.write_vector, &current_clocks.clock)
                     {
@@ -898,6 +900,7 @@ impl VClockAlloc {
 
         // Throw the data-race detection.
         Err(err_machine_stop!(TerminationInfo::DataRace {
+            involves_non_atomic,
             ptr: ptr_dbg,
             op1: RacingOp {
                 action: other_action.to_string(),

src/tools/miri/src/diagnostics.rs

@@ -43,9 +43,10 @@ pub enum TerminationInfo {
         span: SpanData,
     },
     DataRace {
+        involves_non_atomic: bool,
+        ptr: Pointer,
         op1: RacingOp,
         op2: RacingOp,
-        ptr: Pointer,
     },
 }
 
@@ -74,11 +75,15 @@ impl fmt::Display for TerminationInfo {
                 write!(f, "multiple definitions of symbol `{link_name}`"),
             SymbolShimClashing { link_name, .. } =>
                 write!(f, "found `{link_name}` symbol definition that clashes with a built-in shim",),
-            DataRace { ptr, op1, op2 } =>
+            DataRace { involves_non_atomic, ptr, op1, op2 } =>
                 write!(
                     f,
-                    "Data race detected between (1) {} on {} and (2) {} on {} at {ptr:?}. (2) just happened here",
-                    op1.action, op1.thread_info, op2.action, op2.thread_info
+                    "{} detected between (1) {} on {} and (2) {} on {} at {ptr:?}. (2) just happened here",
+                    if *involves_non_atomic { "Data race" } else { "Race condition" },
+                    op1.action,
+                    op1.thread_info,
+                    op2.action,
+                    op2.thread_info
                 ),
         }
     }

src/tools/miri/tests/fail/data_race/mixed_size_read.rs

@@ -19,7 +19,7 @@ fn main() {
         });
         s.spawn(|| {
             a8[0].load(Ordering::SeqCst);
-            //~^ ERROR: Data race detected between (1) 2-byte Atomic Load on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Load on thread `<unnamed>`
+            //~^ ERROR: Race condition detected between (1) 2-byte Atomic Load on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Load on thread `<unnamed>`
         });
     });
 }

src/tools/miri/tests/fail/data_race/mixed_size_read.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: Data race detected between (1) 2-byte Atomic Load on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
+error: Undefined Behavior: Race condition detected between (1) 2-byte Atomic Load on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
   --> $DIR/mixed_size_read.rs:LL:CC
    |
 LL |             a8[0].load(Ordering::SeqCst);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Data race detected between (1) 2-byte Atomic Load on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Race condition detected between (1) 2-byte Atomic Load on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
    |
 help: and (1) occurred earlier here
   --> $DIR/mixed_size_read.rs:LL:CC

src/tools/miri/tests/fail/data_race/mixed_size_write.rs

@@ -19,7 +19,7 @@ fn main() {
         });
         s.spawn(|| {
             a8[0].store(1, Ordering::SeqCst);
-            //~^ ERROR: Data race detected between (1) 2-byte Atomic Store on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Store on thread `<unnamed>`
+            //~^ ERROR: Race condition detected between (1) 2-byte Atomic Store on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Store on thread `<unnamed>`
         });
     });
 }

src/tools/miri/tests/fail/data_race/mixed_size_write.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: Data race detected between (1) 2-byte Atomic Store on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Store on thread `<unnamed>` at ALLOC. (2) just happened here
+error: Undefined Behavior: Race condition detected between (1) 2-byte Atomic Store on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Store on thread `<unnamed>` at ALLOC. (2) just happened here
   --> $DIR/mixed_size_write.rs:LL:CC
    |
 LL |             a8[0].store(1, Ordering::SeqCst);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Data race detected between (1) 2-byte Atomic Store on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Store on thread `<unnamed>` at ALLOC. (2) just happened here
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Race condition detected between (1) 2-byte Atomic Store on thread `<unnamed>` and (2) 1-byte (different-size) Atomic Store on thread `<unnamed>` at ALLOC. (2) just happened here
    |
 help: and (1) occurred earlier here
   --> $DIR/mixed_size_write.rs:LL:CC

src/tools/miri/tests/fail/weak_memory/racing_mixed_size.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: Data race detected between (1) 4-byte Atomic Store on thread `<unnamed>` and (2) 2-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
+error: Undefined Behavior: Race condition detected between (1) 4-byte Atomic Store on thread `<unnamed>` and (2) 2-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
   --> $DIR/racing_mixed_size.rs:LL:CC
    |
 LL |             std::intrinsics::atomic_load_relaxed(hi);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Data race detected between (1) 4-byte Atomic Store on thread `<unnamed>` and (2) 2-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Race condition detected between (1) 4-byte Atomic Store on thread `<unnamed>` and (2) 2-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
    |
 help: and (1) occurred earlier here
   --> $DIR/racing_mixed_size.rs:LL:CC

src/tools/miri/tests/fail/weak_memory/racing_mixed_size_read.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: Data race detected between (1) 4-byte Atomic Load on thread `<unnamed>` and (2) 2-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
+error: Undefined Behavior: Race condition detected between (1) 4-byte Atomic Load on thread `<unnamed>` and (2) 2-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
   --> $DIR/racing_mixed_size_read.rs:LL:CC
    |
 LL |             (*hi).load(Relaxed);
-   |             ^^^^^^^^^^^^^^^^^^^ Data race detected between (1) 4-byte Atomic Load on thread `<unnamed>` and (2) 2-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
+   |             ^^^^^^^^^^^^^^^^^^^ Race condition detected between (1) 4-byte Atomic Load on thread `<unnamed>` and (2) 2-byte (different-size) Atomic Load on thread `<unnamed>` at ALLOC. (2) just happened here
    |
 help: and (1) occurred earlier here
   --> $DIR/racing_mixed_size_read.rs:LL:CC