[5.9][SourceKit] Jump to a background queue before executing SKDUIDFromUIdent
#66442
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…dent` `requestIsEnableBarriers` and `requestIsBarrier` call `SKDUIDFromUIdent`. What I didn’t know, was that `SKDUIDFromUIdent` can send XPC requests to the client to translate UIDs via `sourcekitd_set_uid_handlers`. Since we were calling `requestIsEnableBarriers` directly from the XPC server’s main queue, and the UID handler sends an XPC request synchronously, we could get into a deadlock situation. Immediately jump onto a serial background queue (`msgHandlingQueue`) in `sourcekitdServer_peer_event_handler` so that the main queue is free to execute the UID handler. This more closely matches the behavior before I introduced barriers as well, where we were always immediately jumping onto a concurrrent `msgHandlingQueue`.
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airspeedswift
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Jun 8, 2023
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sourcekitd. We determine whether a request is an open/edit/close fromsourcekitd’s main request handling queue. Checking the request UID might result in an XPC request to the client (to translate strings to numeric UIDs), which could deadlock since we were still using the main request handling queue. Immediately jump onto a serial background queue so that the main queue is free to execute the UID handler.