[SourceKit] Jump to a background queue before executing SKDUIDFromUIdent
#66441
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@swift-ci Please test |
bnbarham
reviewed
Jun 7, 2023
| auto attr = dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_CONCURRENT, | ||
| auto msgHandlingQueueAttr = dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, | ||
| QOS_CLASS_DEFAULT, 0); | ||
| msgHandlingQueue = dispatch_queue_create("request-handling", msgHandlingQueueAttr); |
…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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@swift-ci Please smoke test |
bnbarham
approved these changes
Jun 7, 2023
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requestIsEnableBarriersandrequestIsBarriercallSKDUIDFromUIdent. What I didn’t know, was thatSKDUIDFromUIdentcan send XPC requests to the client to translate UIDs viasourcekitd_set_uid_handlers.Since we were calling
requestIsEnableBarriersdirectly 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) insourcekitdServer_peer_event_handlerso 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 concurrrentmsgHandlingQueue.I think the best way to review this it to look at the combined diff of #66013 and this PR 208eaac...ahoppen:swift:ahoppen/deadlock#diff-0ef1fa70c987d3bee8fd247f1fe85ca4f3ae5ba089da80000753a9cb503ab269