Fix a race condition in TexManager.make_dvi.

anntzer · anntzer · commit 6af8ef0eebe7 · 2025-08-14T13:02:21.000+02:00
Previously, a race condition could occur if, while a process had called
make_tex (generating the tex file in the global cache) and was going to
call the latex subprocess (to generate the dvi file), another process
also called make_tex for the same tex string and started rewriting the
tex source.  In that case, the latex subprocess could see a partially
written (invalid) tex source.

Fix that by generating the tex source in a process-private temporary
directory, where the latex process is already going to run anyways.
(This is cheap compared to the latex subprocess invocation.)
diff --git a/lib/matplotlib/texmanager.py b/lib/matplotlib/texmanager.py
@@ -284,8 +284,10 @@ def make_dvi(cls, tex, fontsize):
         basefile = cls.get_basefile(tex, fontsize)
         dvifile = '%s.dvi' % basefile
         if not os.path.exists(dvifile):
-            texfile = Path(cls.make_tex(tex, fontsize))
-            # Generate the dvi in a temporary directory to avoid race
+            # Also generate the tex source in the main cache directory, but
+            # only for backcompat.
+            cls.make_tex(tex, fontsize)
+            # Generate the tex and dvi in a temporary directory to avoid race
             # conditions e.g. if multiple processes try to process the same tex
             # string at the same time.  Having tmpdir be a subdirectory of the
             # final output dir ensures that they are on the same filesystem,
@@ -296,12 +298,12 @@ def make_dvi(cls, tex, fontsize):
             # will be blocked when `openin_any = p` in texmf.cnf).
             cwd = Path(dvifile).parent
             with TemporaryDirectory(dir=cwd) as tmpdir:
-                tmppath = Path(tmpdir)
+                Path(tmpdir, "file.tex").write_text(
+                    cls._get_tex_source(tex, fontsize), encoding='utf-8')
                 cls._run_checked_subprocess(
                     ["latex", "-interaction=nonstopmode", "--halt-on-error",
-                     f"--output-directory={tmppath.name}",
-                     f"{texfile.name}"], tex, cwd=cwd)
-                (tmppath / Path(dvifile).name).replace(dvifile)
+                     "file.tex"], tex, cwd=tmpdir)
+                Path(tmpdir, "file.dvi").replace(dvifile)
         return dvifile
 
     @classmethod
