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: [email protected]
ReportedBy: [email protected]
--- Comment #0 from safety0ff.bugz <[email protected]> 2013-11-06
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();
}
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