Require Send+Sync bounds for Allocation trait (apache#1945)

arrow/src/alloc/mod.rs

@@ -127,9 +127,9 @@ pub unsafe fn reallocate<T: NativeType>(
 
 /// The owner of an allocation.
 /// The trait implementation is responsible for dropping the allocations once no more references exist.
-pub trait Allocation: RefUnwindSafe {}
+pub trait Allocation: RefUnwindSafe + Send + Sync {}
 
-impl<T: RefUnwindSafe> Allocation for T {}
+impl<T: RefUnwindSafe + Send + Sync> Allocation for T {}
 
 /// Mode of deallocating memory regions
 pub(crate) enum Deallocation {

arrow/src/buffer/immutable.rs

@@ -257,11 +257,6 @@ impl std::ops::Deref for Buffer {
     }
 }
 
-unsafe impl Sync for Buffer {}
-// false positive, see https://github.com/apache/arrow-rs/pull/1169
-#[allow(clippy::non_send_fields_in_send_ty)]
-unsafe impl Send for Buffer {}
-
 impl From<MutableBuffer> for Buffer {
     #[inline]
     fn from(buffer: MutableBuffer) -> Self {

arrow/src/bytes.rs

@@ -101,6 +101,11 @@ impl Bytes {
     }
 }
 
+// Deallocation is Send + Sync, repeating the bound here makes that refactoring safe
+// The only field that is not automatically Send+Sync then is the NonNull ptr
+unsafe impl Send for Bytes where Deallocation: Send {}
+unsafe impl Sync for Bytes where Deallocation: Sync {}
+
 impl Drop for Bytes {
     #[inline]
     fn drop(&mut self) {

arrow/src/ffi.rs

@@ -409,6 +409,9 @@ impl Drop for FFI_ArrowArray {
     }
 }
 
+unsafe impl Send for FFI_ArrowArray {}
+unsafe impl Sync for FFI_ArrowArray {}
+
 // callback used to drop [FFI_ArrowArray] when it is exported
 unsafe extern "C" fn release_array(array: *mut FFI_ArrowArray) {
     if array.is_null() {