RFR: 8251850: Simplify ResourceMark constructors using delegation

[Thomas Stüfe]

On Tue, Aug 18, 2020 at 11:59 AM David Holmes <david.holmes at oracle.com>
wrote:

> On 18/08/2020 7:40 pm, Thomas Stüfe wrote:
> > On Tue, Aug 18, 2020 at 9:52 AM Kim Barrett <kim.barrett at oracle.com
> > <mailto:kim.barrett at oracle.com>> wrote:
> >
> >      > On Aug 17, 2020, at 10:44 PM, David Holmes
> >     <david.holmes at oracle.com <mailto:david.holmes at oracle.com>> wrote:
> >      >
> >      > Hi Kim,
> >      >
> >      > Not a full review - sorry. Have you tested what happens if a
> >     resource leak is introduced? The _warned variable was used, IIUC, to
> >     avoid hitting recursive errors during error reporting.
> >
> >     OH!  The recursive case hadn’t occurred to me!
> >
> >     Poorly named and poorly commented variable from before the beginning
> >     of the mercurial age,
> >     so hard to track down the changeset that introduced it to see if
> >     that shed some light.  Good
> >     thing we have some institutional memory :)
> >
> >     I will do something about that, and then try to figure out how to
> >     trigger it.
> >
> >
> > You could rig up something using -XX:ErrorHandlerTest
> > (VMError::controlled_crash) and allocate from the same ResourceArea
> > again inside the error handler. There are tests for similar things, e.g.
> > SafeFetch, see hotspot/jtreg/runtime/ErrorReporting.
> >
> > But I am not sure this is worthwhile. IMHO it would be better to fix the
> > places where ResourceAreas are used in error reporting instead of muting
> > this warning for recursive calls. Because ideally we do not want
> > allocations to happen at all during error reporting.
>
> I think that is impractical given all the information we try to print as
> part of the error report. I expect a lot of it - e.g register and memory
> contents - to require ResourceMarks (e.g. to print class names).
>
> David
> -----
>
>
All those cases feed from the current Thread's ResourceArea, no? So we
could in theory just place a single ResourceMark at the beginning of
VMError::report() to avoid all those errors (only if we have a current
Thread, of course)?

Thomas