(S) RFR: 8139300: Internal Error (vm/utilities/debug.cpp:399), # Error: ShouldNotReachHere()

[Daniel D. Daugherty]

On 11/11/15 11:33 PM, David Holmes wrote:
> webrev: http://cr.openjdk.java.net/~dholmes/8139300/webrev/

src/share/vm/utilities/debug.cpp
     No comments.

test/runtime/ErrorHandling/SecondaryErrorTest.java
     No comments.

Thumbs up.

Since you've used the POSIX equivalent code:

     pthread_kill(pthread_self(), SIGFPE);

I'm presuming we have no plans to change this code back once
MacOS X fixes the bug in raise().

Dan


>
> Bug report is not public sorry.
>
> In the crash handler test logic in the VM we have:
>
> static void crash_with_sigfpe() {
>    // generate a native synchronous SIGFPE where possible;
>    // if that did not cause a signal (e.g. on ppc), just
>    // raise the signal.
>    volatile int x = 0;
>    volatile int y = 1/x;
>  #ifndef _WIN32
>    raise(SIGFPE);
>  #endif
>  } // end: crash_with_sigfpe
>
> and it is used here:
>
>  402     case 15: crash_with_sigfpe(); break;
>  403
>  404     default: tty->print_cr("ERROR: %d: unexpected test_num 
> value.", how);
>  405   }
>  406   ShouldNotReachHere();
>
> We recently updated the compiler on OSX and started seeing occasional 
> failures of the test exercising this code, the failure mode being that 
> we hit the ShouldNotReachHere() at line #406.
>
> It seems the new compiler may not be generating code for the 
> "y=1/x;"** so we don't get the SIGFPE and so proceed to raise it 
> directly. That then hits an apparent bug on OSX where raise always 
> sends the signal to the main thread not the current thread as required 
> by POSIX in a multi-threaded app. Consequently raise() could return 
> and we'd hit the ShouldNotReachHere().
>
> Whether the test failed or appeared to pass depended on which thread 
> got into the error handler first (though I'm still unclear on the 
> finer details of that potential interaction - the other thread should 
> have seen error reporting was already in progress by the recursively 
> failing thread!)
>
> The solution I chose is to simply convert raise(sig) into its POSIX 
> specified equivalent: pthread_kill(pthreead_self(), sig);
>
> I'm a little reluctant having pthread functions in a shared file, but 
> AFAIK all our platforms supports pthreads. This also doesn't seem any 
> worse than assuming raise() exists on all platforms. But I could add 
> some ifdef _POSIX_C_SOURCE if there is concern (and even have a #error 
> for unknown platforms) ?
>
> ** I'm not surprised a compiler might elide the attempted division by 
> zero. I don't think volatile on a local has any meaning and so could 
> easily be optimized out completely. I overlooked that in the original 
> commit of this logic, and it worked so ...
>
> Thanks,
> David
>