[SR-3300] RunLoop.run() blocks with small time intervals on Linux

[swift-ci]

Previous ID	SR-3300
Radar	None
Original Reporter	zmeyc (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Environment

Swift version 3.0.2 (swift-3.0.2-PREVIEW-1)

Additional Detail from JIRA

Votes	2
Component/s	Foundation
Labels	Bug
Assignee	None
Priority	Medium

md5: bafa9468ae3286e6034cfc307205daa4

Issue Description:

Linux / OS X implementation inconsistency:
If RunLoop.run() is given a very small time interval (such as 0.000001) or zero or negative time interval, it blocks on Linux. On OS X it returns immediately.

import Foundation
import Dispatch

while true {
    print("Loop")
    RunLoop.current.run(mode: RunLoopMode.defaultRunLoopMode, before: Date(timeIntervalSinceNow: 0.000001))
}

"Loop" is printed once, then the app blocks.

[swift-ci]

Comment by Andrey Fidrya (JIRA)

It seems the bug is in:
swift-source/swift-corelibs-foundation/CoreFoundation/RunLoop.subproj/CFRunLoop.c

Replace

        __CFRunLoopServiceFileDescriptors(waitSet, CFPORT_NULL, TIMEOUT_INFINITY, &livePort);

with:

        __CFRunLoopServiceFileDescriptors(waitSet, CFPORT_NULL, poll ? 0 : TIMEOUT_INFINITY, &livePort)

I'll be grateful if someone familiar with libdispatch could check if this is a proper fix.

[swift-ci]

Comment by Andrey Fidrya (JIRA)

Still reproduced on Swift 4.0.2 / Ubuntu 16.

[spevans]

This was fixed in #2544