Address known thread-safety issues in cuda.core/look into call_once pattern

@leofang

In general, cuda.core has a few internal, module-level states that should be guarded by a lock. We haven't done that extensively.

Originally posted by @leofang in #1364 (comment)

Example:

cuda-python/cuda_core/cuda/core/experimental/_launcher.pyx

Lines 20 to 35 in 027ba10

    
           # TODO: revisit this treatment for py313t builds 
        
           _inited = False 
        
           _use_ex = None 
        
           def _lazy_init(): 
        
               global _inited 
        
               if _inited: 
        
                   return 
        
               global _use_ex 
        
               # binding availability depends on cuda-python version 
        
               _py_major_minor = get_binding_version() 
        
               _driver_ver = handle_return(driver.cuDriverGetVersion()) 
        
               _use_ex = (_driver_ver >= 11080) and (_py_major_minor >= (11, 8)) 
        
               _inited = True

Sebastian's comment here is relevant: #1390 (comment)

I did an audit before for this type of issues but will have another sweep soon. Similar code still exists around _decide_nvjitlink_or_driver (and _lazy_init in _linker.pyx), but only a minor issue.

I.e. this doesn't use cdef ... _inited so is no additional free-threading issue. The function may get called twice but looks idempotent except for issuing a warning which is a nuisance.

That said: I'll look into establishing a call-once pattern which wouldn't just fix the nuisance but hopefully also make this clean (or at least obviously so).

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Address known thread-safety issues in `cuda.core`/look into `call_once` pattern #1389

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	# TODO: revisit this treatment for py313t builds
	_inited = False
	_use_ex = None


	def _lazy_init():
	global _inited
	if _inited:
	return

	global _use_ex
	# binding availability depends on cuda-python version
	_py_major_minor = get_binding_version()
	_driver_ver = handle_return(driver.cuDriverGetVersion())
	_use_ex = (_driver_ver >= 11080) and (_py_major_minor >= (11, 8))
	_inited = True

Address known thread-safety issues in cuda.core/look into call_once pattern #1389

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leofang commented on Dec 16, 2025

leofang commented on Dec 17, 2025

seberg commented on Aug 28, 2026

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Address known thread-safety issues in `cuda.core`/look into `call_once` pattern #1389