www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.bugs - [Issue 11454] New: Race in core.thread unit test causing transient failures

reply d-bugmail puremagic.com writes:
https://d.puremagic.com/issues/show_bug.cgi?id=11454

           Summary: Race in core.thread unit test causing transient
                    failures
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: druntime
        AssignedTo: nobody puremagic.com
        ReportedBy: safety0ff.bugz gmail.com



08:36:54 PST ---
The culprit code is from line 2637 of src/core/thread.d [1]
It caused a test failure in an unrelated pull request
(https://d.puremagic.com/test-results/pull.ghtml?projectid=1&runid=779542 ,)
the PR simply removed a no-op and should not have caused any non-failing tests
to begin failing.

My hypothesis is that Thread.sleep is used to yield the secondary thread, but
the secondary thread gets rescheduled before the main thread, causing the first
assertion to fail.

Two solutions I've come up with:
- If the compiler does not treat shared variables as a C compiler treats
"volatile" variables, then we can add a secondary semaphore ensuring the
assertion is executed prior to the secondary thread proceeding.
- Otherwise the assertion is redundant due to the semaphore and can be removed.

[1]
--------------------------------------------
unittest
{
    import core.sync.semaphore;

    shared bool inCriticalRegion;
    auto sem = new Semaphore();

    auto thr = new Thread(
    {
        thread_enterCriticalRegion();
        inCriticalRegion = true;
        sem.notify();
        Thread.sleep(dur!"msecs"(1));
        inCriticalRegion = false;
        thread_exitCriticalRegion();
    });
    thr.start();

    sem.wait();
    assert(inCriticalRegion);
    thread_suspendAll();
    assert(!inCriticalRegion);
    thread_resumeAll();
}
--------------------------------------------

-- 
Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Nov 06 2013
parent d-bugmail puremagic.com writes:
https://d.puremagic.com/issues/show_bug.cgi?id=11454


safety0ff.bugz <safety0ff.bugz gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P2                          |P4
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE



23:44:12 PST ---
Even though I created this report first, I'll mark this one as the duplicate.

*** This issue has been marked as a duplicate of issue 11519 ***

-- 
Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Feb 08 2014