Bug 172390 – [iOS]: RunLoop::main().dispatch() needs to take into account USE_WEB_THREAD

• Status: NEW
• Component: WebCore Misc.

[Joseph Pecoraro]

[iOS]: RunLoop::main().dispatch() needs to take into account WEB_THREAD

There are cases of RunLoop::main().dispatch() in WebCore that may not be safe if USE_WEB_THREAD

    bindings/js/SerializedScriptValue.cpp
    3166:    RunLoop::main().dispatch([this, conditionPtr = &condition, valuePtr = &value] {

    Modules/applepay/ApplePaySession.cpp
    640:        RunLoop::main().dispatch([promise, canMakePayments]() mutable {

    workers/WorkerMessagingProxy.cpp
    168:    RunLoop::main().dispatch([this, protectedThis = makeRef(*this), message = message.isolatedCopy()] {

If possible callOnMainThread could be used or WebThreadRun. See Modules/websockets/WebSocket.cpp's approach.

Note: WorkerMessagingProxy case, callOnMainThread couldn't be used and was specifically avoided.

[Andy Estes]

(In reply to Joseph Pecoraro from comment #0)
>     Modules/applepay/ApplePaySession.cpp
>     640:        RunLoop::main().dispatch([promise, canMakePayments]()
> mutable {
> 

In practice this is safe because Apple Pay is disabled at runtime in WebKit1 clients, so this code won't execute on a WebThread.

I think callOnMainThread() could be used here without a problem, though.

[Anders Carlsson]

RunLoop::main().dispatch() shouldn't be web thread aware since it's used in the UI process. If anything, callOnMainThread should be used in WebCore.

[Chris Dumez]

The call to RunLoop::main().dispatch() in SerializedScriptValue.cpp for IndexedDB does look unsafe and should probably be replaced with callOnMainThread().