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gh-137400: Fix a crash when disabling profiling across all threads (gh-137471)

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The `PyEval_SetProfileAllThreads` function and other related functions
had a race condition on `tstate->c_profilefunc` that could lead to a
crash when disable profiling or tracing on all threads while another
thread is starting to profile or trace a a call.

There are still potential crashes when threads exit concurrently with
profiling or tracing be enabled/disabled across all threads.
This commit is contained in:
Sam Gross
2025-08-11 11:41:44 -04:00
committed by GitHub
parent deb0020e3d
commit 362692852f
3 changed files with 46 additions and 2 deletions
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10
Python/legacy_tracing.c
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@@ -477,13 +477,16 @@ setup_profile(PyThreadState *tstate, Py_tracefunc func, PyObject *arg, PyObject
}
}
_PyEval_StopTheWorld(tstate->interp);
int delta = (func != NULL) - (tstate->c_profilefunc != NULL);
tstate->c_profilefunc = func;
*old_profileobj = tstate->c_profileobj;
tstate->c_profileobj = Py_XNewRef(arg);
tstate->interp->sys_profiling_threads += delta;
assert(tstate->interp->sys_profiling_threads >= 0);
return tstate->interp->sys_profiling_threads;
Py_ssize_t profiling_threads = tstate->interp->sys_profiling_threads;
_PyEval_StartTheWorld(tstate->interp);
return profiling_threads;
}
int
@@ -574,13 +577,16 @@ setup_tracing(PyThreadState *tstate, Py_tracefunc func, PyObject *arg, PyObject
}
}
_PyEval_StopTheWorld(tstate->interp);
int delta = (func != NULL) - (tstate->c_tracefunc != NULL);
tstate->c_tracefunc = func;
*old_traceobj = tstate->c_traceobj;
tstate->c_traceobj = Py_XNewRef(arg);
tstate->interp->sys_tracing_threads += delta;
assert(tstate->interp->sys_tracing_threads >= 0);
return tstate->interp->sys_tracing_threads;
Py_ssize_t tracing_threads = tstate->interp->sys_tracing_threads;
_PyEval_StartTheWorld(tstate->interp);
return tracing_threads;
}
int