Rollup merge of #87507 - jethrogb:jb/sgx-unmoveable-mutex, r=dtolnay

JohnTitor · web-flow · commit 8bc7ec1316b8 · 2021-07-28T18:28:20.000+09:00
SGX mutex is *not* moveable Reverts the erroneous change in #85029.
diff --git a/library/std/src/sys/sgx/mutex.rs b/library/std/src/sys/sgx/mutex.rs
@@ -8,7 +8,8 @@ pub struct Mutex {
     inner: SpinMutex<WaitVariable<bool>>,
 }
 
-pub type MovableMutex = Mutex;
+// not movable: see UnsafeList implementation
+pub type MovableMutex = Box<Mutex>;
 
 // Implementation according to “Operating Systems: Three Easy Pieces”, chapter 28
 impl Mutex {
diff --git a/library/std/src/sys/sgx/waitqueue/unsafe_list.rs b/library/std/src/sys/sgx/waitqueue/unsafe_list.rs
@@ -23,6 +23,7 @@ impl<T> UnsafeListEntry<T> {
     }
 }
 
+// WARNING: self-referential struct!
 pub struct UnsafeList<T> {
     head_tail: NonNull<UnsafeListEntry<T>>,
     head_tail_entry: Option<UnsafeListEntry<T>>,

Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,8 @@ pub struct Mutex {`
`8`	`8`	`inner: SpinMutex<WaitVariable<bool>>,`
`9`	`9`	`}`
`10`	`10`
`11`		`-pub type MovableMutex = Mutex;`
	`11`	`+// not movable: see UnsafeList implementation`
	`12`	`+pub type MovableMutex = Box<Mutex>;`
`12`	`13`
`13`	`14`	`// Implementation according to “Operating Systems: Three Easy Pieces”, chapter 28`
`14`	`15`	`impl Mutex {`
Original file line number	Diff line number	Diff line change
`@@ -23,6 +23,7 @@ impl<T> UnsafeListEntry<T> {`
`23`	`23`	`}`
`24`	`24`	`}`
`25`	`25`
	`26`	`+// WARNING: self-referential struct!`
`26`	`27`	`pub struct UnsafeList<T> {`
`27`	`28`	`head_tail: NonNull<UnsafeListEntry<T>>,`
`28`	`29`	`head_tail_entry: Option<UnsafeListEntry<T>>,`