From: Brett Simmers <swtaarrs@users.noreply.github.com>
Date: Wed, 20 Mar 2024 15:18:26 +0000 (-0700)
Subject: gh-116908: Only write to `_pending_calls.calls_to_do` with atomic operations (#117044)
X-Git-Tag: v3.13.0a6~215
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9221ef2d8cb7f4cf37592eb650d4c8f972033000;p=thirdparty%2FPython%2Fcpython.git

gh-116908: Only write to `_pending_calls.calls_to_do` with atomic operations (#117044)

These writes to `pending->calls_to_do` need to be atomic, because other threads
can read (atomically) from `calls_to_do` without holding `pending->mutex`.
---

diff --git a/Python/ceval_gil.c b/Python/ceval_gil.c
index d2cd35dfa868..78c13d619e6e 100644
--- a/Python/ceval_gil.c
+++ b/Python/ceval_gil.c
@@ -671,7 +671,7 @@ _push_pending_call(struct _pending_calls *pending,
     pending->calls[i].flags = flags;
     pending->last = j;
     assert(pending->calls_to_do < NPENDINGCALLS);
-    pending->calls_to_do++;
+    _Py_atomic_add_int32(&pending->calls_to_do, 1);
     return 0;
 }
 
@@ -701,7 +701,7 @@ _pop_pending_call(struct _pending_calls *pending,
         pending->calls[i] = (struct _pending_call){0};
         pending->first = (i + 1) % NPENDINGCALLS;
         assert(pending->calls_to_do > 0);
-        pending->calls_to_do--;
+        _Py_atomic_add_int32(&pending->calls_to_do, -1);
     }
 }