D 2024-04-19T08:34:54.281
J icomment To\ssummarize\sagain:\r\n\r\n\t1)\sThe\s"problem"\sdescribed\sin\sthis\sticket\sis\sthat\sa\schannel\sis\sbeing\sset\sto\snonblocking\sbefore\sit\sis\sconnected.\s\sThe\sonly\sthing\sthat\sshould\sbe\sdone\swith\sa\schannel\sbefore\sit\sis\sactually\sconnected\sis\sto\swait\sfor\sit\sto\sconnect,\sso\sthe\sreal\sanswer\sto\sthis\sticket\sis,\s"don't\sdo\sthat."\s\sNo\sexample\son\sthe\swiki\shas\sdone\sthat\sin\sthe\slast\s20\syears.\r\n\r\n\t2)\sRegardless\sof\sthat\sargument,\sthe\scode\shas\snow\sbeen\schanged\sso\sthat\ssetting\sa\schannel\sto\snon-blocking\sbefore\sit\sis\sconnected\snow\sbehaves\sas\s"expected".\r\n\r\n\t3)\sAfter\sa\schannel\sevent\shandler\sruns,\sit\sis\snecessary\sto\ssomehow\sreturn\sagain\sto\sthe\sevent\sloop\sbefore\sanother\shandler\sruns\sso\sthat\sthe\sevent\sloop\scan\smediate\sthe\shandling\sof\sevents.\s\sThat's\swhy\sthe\stimer\swas\sintroduced\sback\sin\sthe\sfix\sfor\s[67a5eabbd3].\s\sWithout\sthat,\sreentrancy\sbugs\shappen.\s\sThe\sauthor\sof\sAtom\srecently\swrote\sup\sa\sdescription\sof\sexactly\sthe\ssame\sproblem\sin\s[https://zed.dev/blog/gpui-ownership|Ownership\sand\sdata\sflow\sin\sGPUI]:\r\n\r\n\t<blockquote>This\ssimplicity,\showever,\sled\sto\sa\ssubtle\sbug\sthat\swent\sunnoticed\suntil\sthe\scode\swas\swidely\sused\sin\sproduction.\sThe\sproblem\smanifested\swhen\sone\slistener\sfunction\semitted\san\sevent\sto\sthe\ssame\semitter\sit\swas\ssubscribed\sto.\sThis\sinadvertently\striggered\sreentrancy,\swhere\sthe\semitting\sfunction\swas\scalled\sagain\sbefore\sit\shad\scompleted\sits\sexecution.\sThis\srecursive-like\sbehavior\scontradicted\sour\sexpectation\sof\slinear\sfunction\sexecution\sand\sgot\sus\sinto\san\sunexpected\sstate.\sEven\sthough\sJavaScript's\sgarbage\scollector\senforces\smemory\ssafety,\sthe\slanguage's\srelaxed\sownership\smodel\smade\sit\seasy\sfor\sme\sto\swrite\sthis\sbug.\r\n\r\n\tRust's\sconstraints\smake\sthis\snaive\sapproach\sto\srather\smore\sdifficult.\sWe're\sstrongly\sencouraged\sdown\sa\sdifferent\spath,\swhich\sprevents\sthe\skind\sof\sreetrancy\sI\sdescribed\sabove.\sIn\sGPUI,\swhen\syou\scall\semit\sor\snotify,\sno\slisteners\sare\sinvoked.\sInstead,\swe\spush\sdata\sto\sa\squeue\sof\seffects.\sAt\sthe\send\sof\seach\supdate\swe\sflush\sthese\seffects,\spopping\sfrom\sthe\sfront\sof\sthe\squeue\suntil\sit\sbecomes\sempty\sand\sthen\sreturning\scontrol\sto\sthe\sevent\sloop.\sAny\seffect\shandler\scan\sitself\spush\smore\seffects,\sbut\sthe\ssystem\seventually\squiesces.\sThis\sgives\sus\srun-to-completion\ssemantics\swithout\sreentrancy\sbugs\sand\splays\snicely\swith\sRust.</blockquote>
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