Walk stack in signal handler

[Volker Simonis]

You can use -XX:+PrintOptoAssembly. This option will print out an
abstract assembly for the code it will generate. For every safepoint
(e.g. function call) it will show you the information the JIT has
recorded (i.e. which locals are alive and where they are stored). If
you are not at a safepoint, you can not reliably access a local
variable.

On Thu, Feb 18, 2016 at 4:53 PM, Roman Kovalenko <rmnkvlnk at gmail.com> wrote:
> Hi,
>
> Thank you for the reference. I was already a little familiar with
> PreserveFramePointer but after reading the related mailing list thread I
> have better understanding and it will definitely help me in my future
> researches. The main problem for me for now is that I have poor knowledge of
> where to look for locals of frame that is already found by AsyncGetCallTrace
> and its helpers, because I cannot access locals (or access just 'this' which
> is enough) with calls that are used for same purpose within safepoint (e. g.
> JVMTI GetLocalInstance etc.). I have tried some random workarounds as well,
> but without deeper knowledge they had no success yet. Maybe there was a
> discussion about the stack state outside safepoint? :) Something like that
> would help me a lot, since I have difficulties to get right direction for
> source code reading.
>
> Thanks.
>
> On Wed, Feb 17, 2016 at 7:40 PM, Volker Simonis <volker.simonis at gmail.com>
> wrote:
>>
>> Hi Roman,
>>
>> you should definitely use -XX:+PreserveFramePointer and you should
>> also have a look at the discussion on bug "8068945: Use RBP register
>> as proper frame pointer in JIT compiled code on x86" which discuss
>> some of the difficulties related to native stack walking in hotspot:
>>
>> https://bugs.openjdk.java.net/browse/JDK-8068945
>>
>> Regards,
>> Volker
>>
>>
>> On Wed, Feb 17, 2016 at 6:28 PM, Roman Kovalenko <rmnkvlnk at gmail.com>
>> wrote:
>> > Hi,
>> >
>> > Looks like that I am able to get 'this' for native frame with
>> > frame::get_native_receiver() but I cannot do anything with any other
>> > frame
>> > type.
>> > How can I find out what is permitted to be used outside safepoint? Also,
>> > what can happen to frame outside safepoint, because of what is it hard
>> > to
>> > walk it? May be I should look in some precise source code locations?
>> >
>> > Thanks.
>> >
>> > On Fri, Feb 12, 2016 at 11:48 AM, Andrew Haley <aph at redhat.com> wrote:
>> >
>> >> On 11/02/16 17:54, Roman Kovalenko wrote:
>> >>
>> >> > I would like to profile application by interrupting it with signals
>> >> > and
>> >> > using AsyncGetCallTrace then. This works well, but also I want to
>> >> > collect
>> >> > every 'this' for any object method frame that is walkable by AGCT. I
>> >> looked
>> >> > around (forte.cpp and related) but had no success.
>> >> >
>> >> > Is it even possible?
>> >>
>> >> It's difficult.  The compilers move values around and things are
>> >> really only stable at safepoints.
>> >>
>> >>
>> >
>> >
>> > --
>> > -rmnk-
>
>
>
>
> --
> -rmnk-