RFR: 8271931: Make AbortVMOnVMOperationTimeout more resilient to OS scheduling

[Aleksey Shipilev]

On Thu, 5 Aug 2021 10:45:51 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> After this, we would also not need any other changes here: it would allow to check that task is `NULL` all the same.
>
> Note the fatal msg is different: on VM thread we know the VM-op has completed, but on TimeoutTask the VM-op status is unknown.
> 
> How about sth like this?
> 
> 
> bool check_timeout(jlong& delay) {
>   delay = nanos_to_millis(os::javaTimeNanos() - _arm_time);
>   return delay > AbortVMOnVMOperationTimeoutDelay
> }
> 
> void disarm() {
>   Atomic::release_store_fence(&_armed, 0);
>   
>   jlong delay;
>   if (check_timeout(delay)) {
>     fatal("%s VM operation took too long: completed in " JLONG_FORMAT " ms (timeout: " INTX_FORMAT " ms)",
>         _cur_vm_operation->name(), delay, AbortVMOnVMOperationTimeoutDelay);
>   }
> }

Huh, I missed this difference. Yeah, that goes in the right direction. Can we just pass the `const char*` with the format string to checking method? So we don't do the out-parameter, and the code ends up being:


bool maybe_fail_with(const char* fail_msg) {
  jlong delay = nanos_to_millis(os::javaTimeNanos() - _arm_time);
  if (delay > AbortVMOnVMOperationTimeoutDelay) {
     fatal(fail_msg, delay, AbortVMOnVMOperationTimeoutDelay);
  }
}

void disarm() {
  Atomic::release_store_fence(&_armed, 0);
  maybe_fail_with("VM operation took too long: completed in " JLONG_FORMAT " ms (timeout: " INTX_FORMAT " ms)");
}

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PR: https://git.openjdk.java.net/jdk/pull/5016