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[SR-1639] Move sourcekitdInProc to std::mutex #2793

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[SR-1639] Move sourcekitdInProc to std::mutex #2793

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15 changes: 8 additions & 7 deletions tools/SourceKit/tools/sourcekitd/bin/InProc/sourcekitdInProc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,9 +18,9 @@
#include "llvm/Support/Mutex.h"
#include "llvm/Support/Path.h"

// FIXME: Portability ?
#include <Block.h>
#include <dispatch/dispatch.h>
#include <condition_variable>
#include <mutex>

#ifdef LLVM_ON_WIN32
#include <windows.h>
Expand Down Expand Up @@ -102,16 +102,17 @@ void sourcekitd::set_interrupted_connection_handler(
//===----------------------------------------------------------------------===//

sourcekitd_response_t sourcekitd_send_request_sync(sourcekitd_object_t req) {
dispatch_semaphore_t sema = dispatch_semaphore_create(0);
sourcekitd_response_t ReturnedResp = nullptr;
std::condition_variable handleRequestCondition;

sourcekitd_response_t ReturnedResp;
sourcekitd::handleRequest(req, [&](sourcekitd_response_t resp) {
ReturnedResp = resp;
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Sadly because of spurious wakeup, this assignment now needs to be atomic or it can race with the read below.

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The typical pattern is to use the same mutex to protect writing to the condition being waited on.

dispatch_semaphore_signal(sema);
handleRequestCondition.notify_one();
});

dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
dispatch_release(sema);
std::mutex m;
std::unique_lock<std::mutex> lk(m);
handleRequestCondition.wait(lk, [&]{ return ReturnedResp != nullptr; });
return ReturnedResp;
}

Expand Down