Fix CPython issue #19293 (hangs on AIX).
Fix CPython issue #19293 (hangs on AIX).

gsb-eng/asyncio,haypo/trollius,gsb-eng/asyncio,Martiusweb/asyncio,Martiusweb/asyncio,gsb-eng/asyncio,jashandeep-sohi/asyncio,vxgmichel/asyncio,manipopopo/asyncio,gvanrossum/asyncio,gvanrossum/asyncio,Martiusweb/asyncio,1st1/asyncio,fallen/asyncio,jashandeep-sohi/asyncio,fallen/asyncio,fallen/asyncio,1st1/asyncio,vxgmichel/asyncio,vxgmichel/asyncio,jashandeep-sohi/asyncio,1st1/asyncio,ajdavis/asyncio,ajdavis/asyncio,manipopopo/asyncio,haypo/trollius,manipopopo/asyncio,haypo/trollius,gvanrossum/asyncio,ajdavis/asyncio