RFR(S) 8238585: Use handshake for JvmtiEventControllerPrivate::enter_interp_only_mode() and don't make compiled methods on stack not_entrant

[Reingruber, Richard]

Ok. I will repost and include hotspot runtime and gc lists.

Thanks, Richard.

-----Original Message-----
From: Dean Long <dean.long at oracle.com> 
Sent: Dienstag, 11. Februar 2020 18:28
To: Reingruber, Richard <richard.reingruber at sap.com>; serviceability-dev at openjdk.java.net; hotspot-compiler-dev at openjdk.java.net
Subject: Re: RFR(S) 8238585: Use handshake for JvmtiEventControllerPrivate::enter_interp_only_mode() and don't make compiled methods on stack not_entrant

You might want to have some runtime/GC folks look at the handshake changes.

dl

On 2/6/20 4:39 AM, Reingruber, Richard wrote:
> Hi,
>
> could I please get reviews for this small enhancement:
>
> Webrev: http://cr.openjdk.java.net/~rrich/webrevs/8238585/webrev.0/
> Bug:    https://bugs.openjdk.java.net/browse/JDK-8238585
>
> The change avoids making all compiled methods on stack not_entrant when switching a java thread to
> interpreter only execution for jvmti purposes. It is sufficient to deoptimize the compiled frames on stack.
>
> Additionally a handshake is used instead of a vm operation to walk the stack and do the deoptimizations.
>
> Testing: JCK and JTREG tests, also in Xcomp mode with fastdebug and release builds on all platforms.
>
> Thanks, Richard.
>
> See also my question if anyone knows a reason for making the compiled methods not_entrant:
> http://mail.openjdk.java.net/pipermail/serviceability-dev/2020-January/030339.html