[Webkit-unassigned] [Bug 117842] New: WebProcess hangs loading eff.org (Waiting forever on a sync XHR, NetworkProcess unable to service it)

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=117842

           Summary: WebProcess hangs loading eff.org (Waiting forever on a
                    sync XHR, NetworkProcess unable to service it)
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Macintosh
        OS/Version: All
            Status: ASSIGNED
          Keywords: InRadar
          Severity: Normal
          Priority: P2
         Component: WebKit2
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: beidson at apple.com
                CC: ap at webkit.org, sam at webkit.org


WebProcess hangs loading eff.org (Waiting forever on a sync XHR, NetworkProcess unable to service it)

This is the known theoretical "6 + 1 problem" where 6 asynchronous requests to a host are already outstanding while a 7th sync XHR is made.

In single WebProcess mode and WebKit 1, the sync XHR will time out and the WebProcess will recover.

With the NetworkProcess the WebProcess waits forever on the NetworkProcess, and the NetworkProcess doesn't even try to serve the 7th request.

A lot more could be said about this.  But the TLDR; is that we need to bump the platform connection-per-host limit to 7, and only use that 7th slot for a sync XHR if 6 loads are already in progress.

In radar as <rdar://problem/14112329>

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