[Webkit-unassigned] [Bug 114826] New: ThreadCondition::timedWait should use monotonicallyIncreasingTime

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=114826

           Summary: ThreadCondition::timedWait should use
                    monotonicallyIncreasingTime
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Web Template Framework
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: jmason at blackberry.com
                CC: ap at webkit.org, jmason at blackberry.com, anfraga at qnx.com


Both the pthreads and Windows implementations of ThreadCondition::timedWait use the realtime clock (ie. time returned by currentTime) for their timeout. That means that if the system time changes while timedWait is running, the condition will time out at the wrong time. (For example if the clock is set to after the target time, the condition will time out immediately; if it is set forward by an hour, the condition will not time out until it reaches the original target time, which is now more than an hour in the future.) Interval measurements such as timedWait should be based on the monotonic clock (ie. time returned by monotonicallyIncreasingTime).

That means that the semantics of the absoluteTime parameter would change to take a monotonically increasing value, this change must be reflected in all callers (such as BinarySemaphore::wait and MessageQueue::waitForMessageFilteredWithTimeout), and ultimately the absoluteTime passed to each of these functions must come from a call to monotonicallyIncreasingTime() +- an offset.

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