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

[Reingruber, Richard]

Hi Vladimir,

> > Webrev: http://cr.openjdk.java.net/~rrich/webrevs/8238585/webrev.0/

> Not an expert in JVMTI code base, so can't comment on the actual changes.

>  From JIT-compilers perspective it looks good.

I put out webrev.1 a while ago [1]:

Webrev:        http://cr.openjdk.java.net/~rrich/webrevs/8238585/webrev.1/
Webrev(delta): http://cr.openjdk.java.net/~rrich/webrevs/8238585/webrev.1.inc/

You originally suggested to use a handshake to switch a thread into interpreter mode [2]. I'm using
a direct handshake now, because I think it is the best fit.

May I ask if webrev.1 still looks good to you from JIT-compilers perspective?

Can I list you as (partial) Reviewer?

Thanks, Richard.

[1] http://mail.openjdk.java.net/pipermail/serviceability-dev/2020-April/031245.html
[2] http://mail.openjdk.java.net/pipermail/serviceability-dev/2020-January/030340.html

-----Original Message-----
From: Vladimir Ivanov <vladimir.x.ivanov at oracle.com> 
Sent: Freitag, 7. Februar 2020 09:19
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


> Webrev: http://cr.openjdk.java.net/~rrich/webrevs/8238585/webrev.0/

Not an expert in JVMTI code base, so can't comment on the actual changes.

 From JIT-compilers perspective it looks good.

Best regards,
Vladimir Ivanov

> 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
>