[llvm] dfefc03 - [lit] Explicitly unset timer to free thread stack (#188717)

[via llvm-commits]

Author: Nikita Popov
Date: 2026-03-26T16:57:41+01:00
New Revision: dfefc03769f58d8982202276cd3381356da12dfe

URL: https://github.com/llvm/llvm-project/commit/dfefc03769f58d8982202276cd3381356da12dfe
DIFF: https://github.com/llvm/llvm-project/commit/dfefc03769f58d8982202276cd3381356da12dfe.diff

LOG: [lit] Explicitly unset timer to free thread stack (#188717)

Currently the virtual address space usage of lit fluctuates wildly, with
peak usage exceeding 4GB, which results in subsequent thread spawning
errors on 32-bit systems.

The cause of this is a circular reference in TimeoutHelper._timer (via the
callback), which causes the 8MB thread stack to not be immediately
reclaimed when the timer is cancelled.

We can avoid this by explicitly unsetting the timer.

Added: 
    

Modified: 
    llvm/utils/lit/lit/TestRunner.py

Removed: 
    


################################################################################
diff  --git a/llvm/utils/lit/lit/TestRunner.py b/llvm/utils/lit/lit/TestRunner.py
index d856642e3f447..8bd44a8c30707 100644
--- a/llvm/utils/lit/lit/TestRunner.py
+++ b/llvm/utils/lit/lit/TestRunner.py
@@ -126,6 +126,8 @@ def cancel(self):
         if not self.active():
             return
         self._timer.cancel()
+        # Break reference cycle so that thread stack is freed immediately.
+        self._timer = None
 
     def active(self):
         return self.timeout > 0