Run compiler test suite in parallel on Fuchsia

src/ci/docker/scripts/fuchsia-test-runner.py

@@ -9,6 +9,7 @@ https://doc.rust-lang.org/stable/rustc/platform-support/fuchsia.html#aarch64-unk
 
 import argparse
 from dataclasses import dataclass
+import fcntl
 import glob
 import hashlib
 import json
@@ -146,6 +147,9 @@ class TestEnvironment:
     def zxdb_script_path(self):
         return os.path.join(self.tmp_dir(), "zxdb_script")
 
+    def pm_lockfile_path(self):
+        return os.path.join(self.tmp_dir(), "pm.lock")
+
     def log_info(self, msg):
         print(msg)
 
@@ -460,6 +464,9 @@ class TestEnvironment:
             stderr=self.subprocess_output(),
         )
 
+        # Create lockfiles
+        open(self.pm_lockfile_path(), 'a').close()
+
         # Write to file
         self.write_to_file()
 
@@ -676,19 +683,25 @@ class TestEnvironment:
             log("Publishing package to repo...")
 
             # Publish package to repo
-            subprocess.check_call(
-                [
-                    self.tool_path("pm"),
-                    "publish",
-                    "-a",
-                    "-repo",
-                    self.repo_dir(),
-                    "-f",
-                    far_path,
-                ],
-                stdout=log_file,
-                stderr=log_file,
-            )
+            with open(self.pm_lockfile_path(), 'w') as pm_lockfile:
+                fcntl.lockf(pm_lockfile.fileno(), fcntl.LOCK_EX)
+                subprocess.check_call(
+                    [
+                        self.tool_path("pm"),
+                        "publish",
+                        "-a",
+                        "-repo",
+                        self.repo_dir(),
+                        "-f",
+                        far_path,
+                    ],
+                    stdout=log_file,
+                    stderr=log_file,
+                )
+                # This lock should be released automatically when the pm
+                # lockfile is closed, but we'll be polite and unlock it now
+                # since the spec leaves some wiggle room.
+                fcntl.lockf(pm_lockfile.fileno(), fcntl.LOCK_UN)
 
             log("Running ffx test...")
 

src/doc/rustc/src/platform-support/fuchsia.md

@@ -717,7 +717,7 @@ run the full `tests/ui` test suite:
     --stage=2                                                                 \
     test tests/ui                                                             \
     --target x86_64-unknown-fuchsia                                           \
-    --run=always --jobs 1                                                     \
+    --run=always                                                              \
     --test-args --target-rustcflags                                           \
     --test-args -Lnative=${SDK_PATH}/arch/{x64|arm64}/sysroot/lib             \
     --test-args --target-rustcflags                                           \
@@ -729,9 +729,6 @@ run the full `tests/ui` test suite:
 )
 ```
 
-*Note: The test suite cannot be run in parallel at the moment, so `x.py`
-must be run with `--jobs 1` to ensure only one test runs at a time.*
-
 By default, `x.py` compiles test binaries with `panic=unwind`. If you built your
 Rust toolchain with `-Cpanic=abort`, you need to tell `x.py` to compile test
 binaries with `panic=abort` as well:
@@ -908,7 +905,7 @@ through our `x.py` invocation. The full invocation is:
     --stage=2                                                                 \
     test tests/${TEST}                                                        \
     --target x86_64-unknown-fuchsia                                           \
-    --run=always --jobs 1                                                     \
+    --run=always                                                              \
     --test-args --target-rustcflags                                           \
     --test-args -Lnative=${SDK_PATH}/arch/{x64|arm64}/sysroot/lib             \
     --test-args --target-rustcflags                                           \