Clean up core binding on main thread.

storage-proofs/porep/src/stacked/vanilla/cores.rs

@@ -42,7 +42,25 @@ pub fn checkout_core_group() -> Option<MutexGuard<'static, CoreGroup>> {
     }
 }
 
-pub fn bind_core(core_index: CoreIndex) -> Result<()> {
+pub struct Cleanup {
+    prior_state: Option<hwloc::Bitmap>,
+}
+
+impl Drop for Cleanup {
+    fn drop(&mut self) {
+        match self.prior_state.take() {
+            Some(prior) => {
+                let child_topo = &TOPOLOGY;
+                let tid = get_thread_id();
+                let mut locked_topo = child_topo.lock().unwrap();
+                let _ = locked_topo.set_cpubind_for_thread(tid, prior, CPUBIND_THREAD);
+            }
+            None => (),
+        }
+    }
+}
+
+pub fn bind_core(core_index: CoreIndex) -> Result<Cleanup> {
     let child_topo = &TOPOLOGY;
     let tid = get_thread_id();
     let mut locked_topo = child_topo.lock().unwrap();
@@ -59,6 +77,9 @@ pub fn bind_core(core_index: CoreIndex) -> Result<()> {
     // Get only one logical processor (in case the core is SMT/hyper-threaded).
     bind_to.singlify();
 
+    // Thread binding before explicit set.
+    let before = locked_topo.get_cpubind_for_thread(tid, CPUBIND_THREAD);
+
     debug!("binding to {:?}", bind_to);
     // Set the binding.
     let result = locked_topo
@@ -69,7 +90,9 @@ pub fn bind_core(core_index: CoreIndex) -> Result<()> {
         warn!("error in bind_core, {:?}", result);
     }
 
-    result
+    Ok(Cleanup {
+        prior_state: before,
+    })
 }
 
 fn get_core_by_index<'a>(topo: &'a Topology, index: CoreIndex) -> Result<&'a TopologyObject> {

storage-proofs/porep/src/stacked/vanilla/create_label/multi.rs

@@ -439,14 +439,13 @@ pub fn create_labels_for_encoding<Tree: 'static + MerkleTreeTrait, T: AsRef<[u8]
 
     let core_group = Arc::new(checkout_core_group());
 
-    if let Some(group) = &*core_group {
+    // When `_cleanup_handle` is dropped, the previous binding of thread will be restored.
+    let _cleanup_handle = (*core_group).as_ref().map(|group| {
         // This could fail, but we will ignore the error if so.
         // It will be logged as a warning by `bind_core`.
         debug!("binding core in main thread");
-        if let Some(&core_index) = group.get(0) {
-            let _ = bind_core(core_index);
-        };
-    }
+        group.get(0).map(|core_index| bind_core(*core_index))
+    });
 
     // NOTE: this means we currently keep 2x sector size around, to improve speed
     let (parents_cache, mut layer_labels, mut exp_labels) = setup_create_label_memory(