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[3.14] gh-149156: Fix perf trampoline crash after fork (GH-150347) (#150392)

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Miss Islington (bot) 2026-05-25 20:29:47 +02:00 • committed by GitHub
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commit 152a9a6db4
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2 changed files with 15 additions and 5 deletions
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3
Misc/NEWS.d/next/Core_and_Builtins/2026-05-24-14-45-00.gh-issue-149156.NP73rB.rst Normal file
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@ -0,0 +1,3 @@
Fix an intermittent crash after :func:`os.fork` when perf trampoline
profiling is enabled and the child returns through trampoline frames
inherited from the parent process.

17
Python/perf_trampoline.c
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@ -211,9 +211,8 @@ enum perf_trampoline_type {
static void free_code_arenas(void);
static void
perf_trampoline_reset_state(void)
perf_trampoline_clear_code_watcher(void)
{
free_code_arenas();
if (code_watcher_id >= 0) {
PyCode_ClearWatcher(code_watcher_id);
code_watcher_id = -1;
@ -221,6 +220,13 @@ perf_trampoline_reset_state(void)
extra_code_index = -1;
}
static void
perf_trampoline_reset_state(void)
{
free_code_arenas();
perf_trampoline_clear_code_watcher();
}
static int
perf_trampoline_code_watcher(PyCodeEvent event, PyCodeObject *co)
{
@ -623,9 +629,10 @@ _PyPerfTrampoline_AfterFork_Child(void)
// After fork, Fini may leave the old code watcher registered
// if trampolined code objects from the parent still exist
// (trampoline_refcount > 0). Clear it unconditionally before
// Init registers a new one, to prevent two watchers sharing
// the same globals and double-decrementing trampoline_refcount.
perf_trampoline_reset_state();
// Init registers a new one, but keep the old arenas mapped: the
// child may still need to return through trampoline frames that
// were on the C stack at fork().
perf_trampoline_clear_code_watcher();
_PyPerfTrampoline_Init(1);
}
}