Bug 133708 – Make it possible for waitForAndDispatchImmediately to bail if a sync message comes in from the other direction

• Component: WebKit2
• Status: RESOLVED FIXED

[Tim Horton]

We should have a flag on waitForAndDispatchImmediately that makes it bail immediately if a sync message comes in from the other direction. For example:

1. UI process is waitForAndDispatchImmediatelying, waiting for message X from the Web process
2. Web process timer fires, sends sync message Y to the UI process. Y won't return until the UI process main thread gets a chance to run, but it's currently waiting.
<a long time goes by with both processes doing nothing useful>
3. *Eventually* we hit the waitForAndDispatchImmediately timeout, and everything proceeds normally from there.

Instead:

1. UI process is waitForAndDispatchImmediatelying, waiting for message X from the Web process
2. Web process timer fires, sends sync message Y to the UI process.
3. The waitForAndDispatchImmediately on message X bails immediately.
4. Message Y is handled.
<a long time didn't have to go by>

[Tim Horton]

Created attachment 232833 [details]
patch

[Tim Horton]

Created attachment 232834 [details]
patch

[Anders Carlsson]

Comment on attachment 232834 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=232834&action=review

> Source/WebKit2/Platform/IPC/Connection.cpp:392
> +    WaitForMessageInfo waitingForMessage(messageReceiverName, messageName, destinationID, flags);

There's still no run loop assertion here!

> Source/WebKit2/Platform/IPC/Connection.h:172
> +    template<typename T> bool waitForAndDispatchImmediately(uint64_t destinationID, std::chrono::milliseconds timeout, WaitForMessageFlags = (WaitForMessageFlags)0);

Please use an unsigned instead of the cast.

> Source/WebKit2/Platform/IPC/Connection.h:280
> +    struct WaitForMessageInfo {
> +        WaitForMessageInfo(StringReference messageReceiverName, StringReference messageName, uint64_t destinationID, WaitForMessageFlags flags)
> +            : messageReceiverName(messageReceiverName)
> +            , messageName(messageName)
> +            , destinationID(destinationID)
> +            , waitForMessageFlags(flags)
> +        { }
> +
> +        StringReference messageReceiverName;
> +        StringReference messageName;
> +        uint64_t destinationID;
> +
> +        WaitForMessageFlags waitForMessageFlags;
> +        bool messageWaitingInterrupted = false;
> +
> +        std::unique_ptr<MessageDecoder> decoder;
> +    };
> +
> +    WaitForMessageInfo* m_waitingForMessage;

I think you can forward declare this and just stick it in the .cpp file. Maybe call it WaitForMessageState?

[Tim Horton]

Created attachment 232891 [details]
anders changes

[Anders Carlsson]

Comment on attachment 232891 [details]
anders changes

View in context: https://bugs.webkit.org/attachment.cgi?id=232891&action=review

> Source/WebKit2/Platform/IPC/Connection.cpp:45
> +    { }

Newline after {

> Source/WebKit2/Platform/IPC/Connection.cpp:428
> +            std::unique_ptr<MessageDecoder> decoder = std::move(m_waitingForMessage->decoder);

auto decoder =

[Tim Horton]

http://trac.webkit.org/changeset/169825