From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Thu, 16 Jan 2020 23:28:03 +0000 (-0500)
Subject: Pop thread token requests from the front
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=1988dd92b8c5e0f04a415973e7d42277ed41bdc1;p=cargo.git

Pop thread token requests from the front

This ensures we have a first come first served ordering for both thread and
process tokens.
---

diff --git a/src/cargo/core/compiler/job_queue.rs b/src/cargo/core/compiler/job_queue.rs
index 4bde576dd..5411579f1 100644
--- a/src/cargo/core/compiler/job_queue.rs
+++ b/src/cargo/core/compiler/job_queue.rs
@@ -425,7 +425,10 @@ impl<'a, 'cfg> DrainState<'a, 'cfg> {
         // If we managed to acquire some extra tokens, send them off to a waiting rustc.
         let extra_tokens = self.tokens.len() - (self.active.len() - 1);
         for _ in 0..extra_tokens {
-            if let Some((id, client)) = self.to_send_clients.pop() {
+            if !self.to_send_clients.is_empty() {
+                // remove from the front so we grant the token to the oldest
+                // waiter
+                let (id, client) = self.to_send_clients.remove(0);
                 let token = self.tokens.pop().expect("an extra token");
                 self.rustc_tokens
                     .entry(id)