sync support: dont implicitly clone inside the general sync machinery

Author: RalfJung

src/tools/miri/src/concurrency/sync.rs

@@ -221,12 +221,16 @@ impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
 pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     /// Helper for lazily initialized `alloc_extra.sync` data:
     /// this forces an immediate init.
-    fn lazy_sync_init<T: 'static>(
-        &mut self,
+    /// Return a reference to the data in the machine state.
+    fn lazy_sync_init<'a, T: 'static>(
+        &'a mut self,
         primitive: &MPlaceTy<'tcx>,
         init_offset: Size,
         data: T,
-    ) -> InterpResult<'tcx> {
+    ) -> InterpResult<'tcx, &'a T>
+    where
+        'tcx: 'a,
+    {
         let this = self.eval_context_mut();
 
         let (alloc, offset, _) = this.ptr_get_alloc_id(primitive.ptr(), 0)?;
@@ -239,7 +243,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             &init_field,
             AtomicWriteOrd::Relaxed,
         )?;
-        interp_ok(())
+        interp_ok(this.get_alloc_extra(alloc)?.get_sync::<T>(offset).unwrap())
     }
 
     /// Helper for lazily initialized `alloc_extra.sync` data:
@@ -248,15 +252,17 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     ///   and stores that in `alloc_extra.sync`.
     /// - Otherwise, calls `new_data` to initialize the primitive.
     ///
-    /// The return value is a *clone* of the stored data, so if you intend to mutate it
-    /// better wrap everything into an `Rc`.
-    fn lazy_sync_get_data<T: 'static + Clone>(
-        &mut self,
+    /// Return a reference to the data in the machine state.
+    fn lazy_sync_get_data<'a, T: 'static>(
+        &'a mut self,
         primitive: &MPlaceTy<'tcx>,
         init_offset: Size,
         missing_data: impl FnOnce() -> InterpResult<'tcx, T>,
         new_data: impl FnOnce(&mut MiriInterpCx<'tcx>) -> InterpResult<'tcx, T>,
-    ) -> InterpResult<'tcx, T> {
+    ) -> InterpResult<'tcx, &'a T>
+    where
+        'tcx: 'a,
+    {
         let this = self.eval_context_mut();
 
         // Check if this is already initialized. Needs to be atomic because we can race with another
@@ -280,17 +286,15 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             // or else it has been moved illegally.
             let (alloc, offset, _) = this.ptr_get_alloc_id(primitive.ptr(), 0)?;
             let (alloc_extra, _machine) = this.get_alloc_extra_mut(alloc)?;
-            if let Some(data) = alloc_extra.get_sync::<T>(offset) {
-                interp_ok(data.clone())
-            } else {
+            // Due to borrow checker reasons, we have to do the lookup twice.
+            if alloc_extra.get_sync::<T>(offset).is_none() {
                 let data = missing_data()?;
-                alloc_extra.sync.insert(offset, Box::new(data.clone()));
-                interp_ok(data)
+                alloc_extra.sync.insert(offset, Box::new(data));
             }
+            interp_ok(alloc_extra.get_sync::<T>(offset).unwrap())
         } else {
             let data = new_data(this)?;
-            this.lazy_sync_init(primitive, init_offset, data.clone())?;
-            interp_ok(data)
+            this.lazy_sync_init(primitive, init_offset, data)
         }
     }
 
@@ -326,7 +330,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
     #[inline]
     /// Get the id of the thread that currently owns this lock.
-    fn mutex_get_owner(&mut self, mutex_ref: &MutexRef) -> ThreadId {
+    fn mutex_get_owner(&self, mutex_ref: &MutexRef) -> ThreadId {
         mutex_ref.0.borrow().owner.unwrap()
     }
 

src/tools/miri/src/shims/unix/macos/sync.rs

@@ -22,10 +22,13 @@ enum MacOsUnfairLock {
 
 impl<'tcx> EvalContextExtPriv<'tcx> for crate::MiriInterpCx<'tcx> {}
 trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
-    fn os_unfair_lock_get_data(
-        &mut self,
+    fn os_unfair_lock_get_data<'a>(
+        &'a mut self,
         lock_ptr: &OpTy<'tcx>,
-    ) -> InterpResult<'tcx, MacOsUnfairLock> {
+    ) -> InterpResult<'tcx, &'a MacOsUnfairLock>
+    where
+        'tcx: 'a,
+    {
         let this = self.eval_context_mut();
         let lock = this.deref_pointer(lock_ptr)?;
         this.lazy_sync_get_data(
@@ -68,6 +71,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             );
             return interp_ok(());
         };
+        let mutex_ref = mutex_ref.clone();
 
         if this.mutex_is_locked(&mutex_ref) {
             if this.mutex_get_owner(&mutex_ref) == this.active_thread() {
@@ -97,6 +101,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             this.write_scalar(Scalar::from_bool(false), dest)?;
             return interp_ok(());
         };
+        let mutex_ref = mutex_ref.clone();
 
         if this.mutex_is_locked(&mutex_ref) {
             // Contrary to the blocking lock function, this does not check for
@@ -119,6 +124,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 "attempted to unlock an os_unfair_lock not owned by the current thread".to_owned()
             ));
         };
+        let mutex_ref = mutex_ref.clone();
 
         // Now, unlock.
         if this.mutex_unlock(&mutex_ref)?.is_none() {
@@ -147,6 +153,8 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 "called os_unfair_lock_assert_owner on an os_unfair_lock not owned by the current thread".to_owned()
             ));
         };
+        let mutex_ref = mutex_ref.clone();
+
         if !this.mutex_is_locked(&mutex_ref)
             || this.mutex_get_owner(&mutex_ref) != this.active_thread()
         {
@@ -167,6 +175,8 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             // The lock is poisoned, who knows who owns it... we'll pretend: someone else.
             return interp_ok(());
         };
+        let mutex_ref = mutex_ref.clone();
+
         if this.mutex_is_locked(&mutex_ref)
             && this.mutex_get_owner(&mutex_ref) == this.active_thread()
         {

src/tools/miri/src/shims/unix/sync.rs

@@ -185,7 +185,10 @@ fn mutex_create<'tcx>(
 fn mutex_get_data<'tcx, 'a>(
     ecx: &'a mut MiriInterpCx<'tcx>,
     mutex_ptr: &OpTy<'tcx>,
-) -> InterpResult<'tcx, PthreadMutex> {
+) -> InterpResult<'tcx, &'a PthreadMutex>
+where
+    'tcx: 'a,
+{
     let mutex = ecx.deref_pointer(mutex_ptr)?;
     ecx.lazy_sync_get_data(
         &mutex,
@@ -259,10 +262,13 @@ fn rwlock_init_offset<'tcx>(ecx: &MiriInterpCx<'tcx>) -> InterpResult<'tcx, Size
     interp_ok(offset)
 }
 
-fn rwlock_get_data<'tcx>(
-    ecx: &mut MiriInterpCx<'tcx>,
+fn rwlock_get_data<'tcx, 'a>(
+    ecx: &'a mut MiriInterpCx<'tcx>,
     rwlock_ptr: &OpTy<'tcx>,
-) -> InterpResult<'tcx, PthreadRwLock> {
+) -> InterpResult<'tcx, &'a PthreadRwLock>
+where
+    'tcx: 'a,
+{
     let rwlock = ecx.deref_pointer(rwlock_ptr)?;
     ecx.lazy_sync_get_data(
         &rwlock,
@@ -389,10 +395,13 @@ fn cond_create<'tcx>(
     interp_ok(data)
 }
 
-fn cond_get_data<'tcx>(
-    ecx: &mut MiriInterpCx<'tcx>,
+fn cond_get_data<'tcx, 'a>(
+    ecx: &'a mut MiriInterpCx<'tcx>,
     cond_ptr: &OpTy<'tcx>,
-) -> InterpResult<'tcx, PthreadCondvar> {
+) -> InterpResult<'tcx, &'a PthreadCondvar>
+where
+    'tcx: 'a,
+{
     let cond = ecx.deref_pointer(cond_ptr)?;
     ecx.lazy_sync_get_data(
         &cond,
@@ -498,7 +507,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     ) -> InterpResult<'tcx> {
         let this = self.eval_context_mut();
 
-        let mutex = mutex_get_data(this, mutex_op)?;
+        let mutex = mutex_get_data(this, mutex_op)?.clone();
 
         let ret = if this.mutex_is_locked(&mutex.mutex_ref) {
             let owner_thread = this.mutex_get_owner(&mutex.mutex_ref);
@@ -535,7 +544,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     fn pthread_mutex_trylock(&mut self, mutex_op: &OpTy<'tcx>) -> InterpResult<'tcx, Scalar> {
         let this = self.eval_context_mut();
 
-        let mutex = mutex_get_data(this, mutex_op)?;
+        let mutex = mutex_get_data(this, mutex_op)?.clone();
 
         interp_ok(Scalar::from_i32(if this.mutex_is_locked(&mutex.mutex_ref) {
             let owner_thread = this.mutex_get_owner(&mutex.mutex_ref);
@@ -561,7 +570,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     fn pthread_mutex_unlock(&mut self, mutex_op: &OpTy<'tcx>) -> InterpResult<'tcx, Scalar> {
         let this = self.eval_context_mut();
 
-        let mutex = mutex_get_data(this, mutex_op)?;
+        let mutex = mutex_get_data(this, mutex_op)?.clone();
 
         if let Some(_old_locked_count) = this.mutex_unlock(&mutex.mutex_ref)? {
             // The mutex was locked by the current thread.
@@ -590,7 +599,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         // Reading the field also has the side-effect that we detect double-`destroy`
         // since we make the field unint below.
-        let mutex = mutex_get_data(this, mutex_op)?;
+        let mutex = mutex_get_data(this, mutex_op)?.clone();
 
         if this.mutex_is_locked(&mutex.mutex_ref) {
             throw_ub_format!("destroyed a locked mutex");
@@ -822,8 +831,8 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     ) -> InterpResult<'tcx> {
         let this = self.eval_context_mut();
 
-        let data = cond_get_data(this, cond_op)?;
-        let mutex_ref = mutex_get_data(this, mutex_op)?.mutex_ref;
+        let data = *cond_get_data(this, cond_op)?;
+        let mutex_ref = mutex_get_data(this, mutex_op)?.mutex_ref.clone();
 
         this.condvar_wait(
             data.id,
@@ -846,8 +855,8 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     ) -> InterpResult<'tcx> {
         let this = self.eval_context_mut();
 
-        let data = cond_get_data(this, cond_op)?;
-        let mutex_ref = mutex_get_data(this, mutex_op)?.mutex_ref;
+        let data = *cond_get_data(this, cond_op)?;
+        let mutex_ref = mutex_get_data(this, mutex_op)?.mutex_ref.clone();
 
         // Extract the timeout.
         let duration = match this

src/tools/miri/src/shims/windows/sync.rs

@@ -20,10 +20,13 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
     // Windows sync primitives are pointer sized.
     // We only use the first 4 bytes for the id.
 
-    fn init_once_get_data(
-        &mut self,
+    fn init_once_get_data<'a>(
+        &'a mut self,
         init_once_ptr: &OpTy<'tcx>,
-    ) -> InterpResult<'tcx, WindowsInitOnce> {
+    ) -> InterpResult<'tcx, &'a WindowsInitOnce>
+    where
+        'tcx: 'a,
+    {
         let this = self.eval_context_mut();
 
         let init_once = this.deref_pointer(init_once_ptr)?;