From 7b69a6271e3e1469da26dce61284dbcb1face302 Mon Sep 17 00:00:00 2001
From: David Cook <divergentdave@gmail.com>
Date: Sat, 18 Apr 2020 19:31:02 -0500
Subject: [PATCH] Add support for std::thread::yield_now

---
 src/shims/foreign_items/posix.rs   | 3 +++
 src/shims/foreign_items/windows.rs | 5 +++++
 tests/run-pass/sync.rs             | 5 +++++
 3 files changed, 13 insertions(+)

diff --git a/src/shims/foreign_items/posix.rs b/src/shims/foreign_items/posix.rs
index 3ececb9c20bb..35decd6ddbf2 100644
--- a/src/shims/foreign_items/posix.rs
+++ b/src/shims/foreign_items/posix.rs
@@ -312,6 +312,9 @@ fn emulate_foreign_item_by_name(
                 // We do not support forking, so there is nothing to do here.
                 this.write_null(dest)?;
             }
+            "sched_yield" => {
+                this.write_null(dest)?;
+            }
 
             // Incomplete shims that we "stub out" just to get pre-main initialization code to work.
             // These shims are enabled only when the caller is in the standard library.
diff --git a/src/shims/foreign_items/windows.rs b/src/shims/foreign_items/windows.rs
index 1d17cbcefdee..0125127a9f40 100644
--- a/src/shims/foreign_items/windows.rs
+++ b/src/shims/foreign_items/windows.rs
@@ -201,6 +201,11 @@ fn emulate_foreign_item_by_name(
                 // FIXME: we should set last_error, but to what?
                 this.write_null(dest)?;
             }
+            "SwitchToThread" => {
+                // Note that once Miri supports concurrency, this will need to return a nonzero
+                // value if this call does result in switching to another thread.
+                this.write_null(dest)?;
+            }
 
             // Better error for attempts to create a thread
             "CreateThread" => {
diff --git a/tests/run-pass/sync.rs b/tests/run-pass/sync.rs
index 90885880e681..a4fd6f584c58 100644
--- a/tests/run-pass/sync.rs
+++ b/tests/run-pass/sync.rs
@@ -10,6 +10,7 @@ fn main() {
         test_rwlock_stdlib();
     }
     test_spin_loop_hint();
+    test_thread_yield_now();
 }
 
 fn test_mutex_stdlib() {
@@ -56,3 +57,7 @@ fn would_block(&self) -> bool {
 fn test_spin_loop_hint() {
     atomic::spin_loop_hint();
 }
+
+fn test_thread_yield_now() {
+    std::thread::yield_now();
+}