(S) RFR: 8159461: bigapps/Kitchensink/stressExitCode hits assert: Must be VMThread or JavaThread
david.holmes at oracle.com
Fri Aug 5 02:28:47 UTC 2016
Thanks for looking at this.
On 5/08/2016 1:48 AM, Volker Simonis wrote:
> Hi David,
> thanks for doing this change on all platforms.
> The fix looks good. Maybe you can just extend the following comment with
> something like:
> // Note that the SR_lock plays no role in this suspend/resume protocol.
> // It is only used in SR_handler as a thread termination indicator if
Darn this code is confusing - too many "SR"'s :( I have added
// Note that the SR_lock plays no role in this suspend/resume protocol,
// but is checked for NULL in SR_handler as a thread termination indicator.
This also reminded me to follow up on why the Solaris SR_handler is
different and I found it is not actually installed as a direct signal
handler, but is called from the real signal handler if dealing with a
JavaThread or the VMThread. Consequently the Solaris version of the
SR_handler can not encounter this specific bug and so I have reverted
the changes to os_solaris.cpp
> On Wed, Aug 3, 2016 at 3:13 AM, David Holmes <david.holmes at oracle.com
> <mailto:david.holmes at oracle.com>> wrote:
> webrev: http://cr.openjdk.java.net/~dholmes/8159461/webrev/
> bug: https://bugs.openjdk.java.net/browse/JDK-8159461
> The suspend/resume signal (SR_signum) is never sent to a thread once
> it has started to terminate. On one platform (SuSE 12) we have seen
> what appears to be a "stuck" signal, which is only delivered when
> the terminating thread restores its original signal mask (as if
> pthread_sigmask makes the system realize there is a pending signal -
> we already check the signal was not blocked). At this point in the
> thread termination we have freed the osthread, so the the SR_handler
> would access deallocated memory. In debug builds we first hit an
> assertion that the current thread is a JavaThread or the VMThread -
> that assertion fails, even though it is a JavaThread, because we
> have already executed the ~JavaThread destructor and inside the
> ~Thread destructor we are a plain Thread not a JavaThread.
> The fix was to make a small adjustment to the thread termination
> process so that we delete the SR_lock before calling
> os::free_thread(). In the SR_handler() we can then use a NULL check
> of SR_lock() to indicate the thread has terminated and we return.
> While only seen on Linux I took the opportunity to apply the fix on
> all platforms and also cleaned up the code where we were using
> Thread::current() unsafely in a signal-handling context.
> Testing: regular tier 1 (JPRT)
> Kitchensink (in progress)
> As we can't readily reproduce the problem I tested this by having a
> terminating thread raise SR_signum directly from within the ~Thread
More information about the hotspot-runtime-dev