progress: Fix race condition causing fileno crash
A race condition occurs when sync redirects sys.stderr to capture worker output, while a background progress thread simultaneously calls fileno() on it. This causes an io.UnsupportedOperation error. Fix by caching the original sys.stderr for all progress bar IO.
Change-Id: Idb1f45d707596d31238a19fd373cac3bf669c405
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/498121
Tested-by: Gavin Mak <gavinmak@google.com>
Reviewed-by: Scott Lee <ddoman@google.com>
diff --git a/progress.py b/progress.py
index 30ec8c3..9a91dcd 100644
--- a/progress.py
+++ b/progress.py
@@ -25,7 +25,10 @@
from repo_trace import IsTraceToStderr
-_TTY = sys.stderr.isatty()
+# Capture the original stderr stream. We use this exclusively for progress
+# updates to ensure we talk to the terminal even if stderr is redirected.
+_STDERR = sys.stderr
+_TTY = _STDERR.isatty()
# This will erase all content in the current line (wherever the cursor is).
# It does not move the cursor, so this is usually followed by \r to move to
@@ -133,11 +136,11 @@
def _write(self, s):
s = "\r" + s
if self._elide:
- col = os.get_terminal_size(sys.stderr.fileno()).columns
+ col = os.get_terminal_size(_STDERR.fileno()).columns
if len(s) > col:
s = s[: col - 1] + ".."
- sys.stderr.write(s)
- sys.stderr.flush()
+ _STDERR.write(s)
+ _STDERR.flush()
def start(self, name):
self._active += 1
@@ -211,9 +214,9 @@
# Erase the current line, print the message with a newline,
# and then immediately redraw the progress bar on the new line.
- sys.stderr.write("\r" + CSI_ERASE_LINE)
- sys.stderr.write(msg + "\n")
- sys.stderr.flush()
+ _STDERR.write("\r" + CSI_ERASE_LINE)
+ _STDERR.write(msg + "\n")
+ _STDERR.flush()
self.update(inc=0)
def end(self):
