Possibility of integer overflow in JfrThreadSampler::run()

[末永 恭正]

Hi all,

I tried JFR: `java -XX:StartFlightRecording=dumponexit=true,filename=test.jfr --version` with fastdebug VM, but it crashed.
I uploaded hs_err log here:

   http://cr.openjdk.java.net/~ysuenaga/jfr-integer-overflow/hs_err_pid46934.log

I encountered this crash on Fedora 28 x64. VM was built with GCC 8.1 .

I checked core image, and I found possibility of integer overflow in JfrThreadSampler::run().
I paste GDB frame info:

```
(gdb) f 24
#24 0x00007f657a5937b7 in os::naked_short_sleep (ms=9223372036854775807)
     at /home/ysuenaga/OpenJDK/jdk/src/hotspot/os/linux/os_linux.cpp:4076
4076      assert(ms < 1000, "Un-interruptable sleep, short time use only");
(gdb) p/x ms
$1 = 0x7fffffffffffffff
```

Frame #24 is an assertion which is caused this crash.
`ms` is max_jlong.
JfrThreadSampler::run() calculates `next_j` and `next_n` to calculate sleep time, but it might be overflowed.

So I think it can be fixed as below:
   http://cr.openjdk.java.net/~ysuenaga/jfr-integer-overflow/webrev/

Can it be accepted as a bug? If so, I will file it to JBS and will send review request.


Thanks,

Yasumasa