Rollup merge of #92559 - durin42:llvm-14-attributemask, r=nikic

[rust.git] / src / bootstrap / bootstrap.py

diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 5df3d0bde6d58725cb4715b640614dbb9b921720..5235a6b8180533ea4269aa35ef423fdeb65637eb 100644 (file)
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -15,6 +15,42 @@ import tempfile
 
 from time import time
 
+# Acquire a lock on the build directory to make sure that
+# we don't cause a race condition while building
+# Lock is created in `build_dir/lock.db`
+def acquire_lock(build_dir):
+    try:
+        import sqlite3
+
+        path = os.path.join(build_dir, "lock.db")
+        try:
+            con = sqlite3.Connection(path, timeout=0)
+            curs = con.cursor()
+            curs.execute("BEGIN EXCLUSIVE")
+            # The lock is released when the cursor is dropped
+            return curs
+        # If the database is busy then lock has already been acquired
+        # so we wait for the lock.
+        # We retry every quarter second so that execution is passed back to python
+        # so that it can handle signals
+        except sqlite3.OperationalError:
+            del con
+            del curs
+            print("Waiting for lock on build directory")
+            con = sqlite3.Connection(path, timeout=0.25)
+            curs = con.cursor()
+            while True:
+                try:
+                    curs.execute("BEGIN EXCLUSIVE")
+                except sqlite3.OperationalError:
+                    pass
+            return curs
+    except ImportError:
+        print("warning: sqlite3 not available in python, skipping build directory lock")
+        print("please file an issue on rust-lang/rust")
+        print("this is not a problem for non-concurrent x.py invocations")
+        return None
+
 def support_xz():
     try:
         with tempfile.NamedTemporaryFile(delete=False) as temp_file:
@@ -938,6 +974,7 @@ class RustBuild(object):
 
     def build_bootstrap(self):
         """Build bootstrap"""
+        print("Building rustbuild")
         build_dir = os.path.join(self.build_dir, "bootstrap")
         if self.clean and os.path.exists(build_dir):
             shutil.rmtree(build_dir)
@@ -1097,7 +1134,7 @@ class RustBuild(object):
             recorded_submodules[data[3]] = data[2]
         for module in filtered_submodules:
             self.update_submodule(module[0], module[1], recorded_submodules)
-        print("Submodules updated in %.2f seconds" % (time() - start_time))
+        print("  Submodules updated in %.2f seconds" % (time() - start_time))
 
     def set_dist_environment(self, url):
         """Set download URL for normal environment"""
@@ -1228,6 +1265,12 @@ def bootstrap(help_triggered):
     build.set_dist_environment(data["dist_server"])
 
     build.build = args.build or build.build_triple()
+
+    # Acquire the lock before doing any build actions
+    # The lock is released when `lock` is dropped
+    if not os.path.exists(build.build_dir):
+        os.makedirs(build.build_dir)
+    lock = acquire_lock(build.build_dir)
     build.update_submodules()
 
     # Fetch/build the bootstrap