[aarch64-port-dev ] RFR: fix for crash caused by earlyret of compiled method

[Sergey Nazarkin]

Hi Andrew,

we are at top frame, but temps and extra_args are 0

#0  AbstractInterpreter::size_activation (max_stack=3, temps=0, extra_args=0, monitors=1, callee_params=0, callee_locals=0,
    is_top_frame=true) at /media/psf/Home/projects/zulu8-arm64-dev/hotspot/src/cpu/aarch64/vm/templateInterpreter_aarch64.cpp:1635
#1  0x0000007fb78c6b10 in vframeArrayElement::on_stack_size (this=0x7f840014b8, callee_parameters=0, callee_locals=0,
    is_top_frame=true, popframe_extra_stack_expression_els=0)
    at /media/psf/Home/projects/zulu8-arm64-dev/hotspot/src/share/vm/runtime/vframeArray.cpp:442


Sergey Nazarkin




> On 13 Jun 2017, at 17:54, Andrew Haley <aph at redhat.com> wrote:
> 
> On 13/06/17 14:24, Sergey Nazarkin wrote:
>> Hi!
>> 
>> Please review the fix [1] for the crash happens when compiled method is forced to return early.  We found this issue when running vm/jvmti/ForceEarlyReturnObject/fero001/fero00103/fero00103.html JCK test on CPU with 47 cores. 
>> 
>> The crash happens at the time when test  code tries to check returned value and gets invalid oop.  Despite correct object was acquired by load_earlyret_value(), it is  accidentally substituted on the stack when remove_activation() is executed (see TemplateInterpreterGenerator::generate_earlyret_entry_for). Substitution, in turns, happens due to overlapping of expression and native stacks. Particularly esp equals to sp because frame with no expression is restored (that is correct).  
>> 
>> After that execution of following code sequence replaces TOS with  some irrelevant value. 
>> 
>> push(tos)  // -> puts value on expression stack
>> unlock_object() // -> calls call_VM() and save registers on native stack, in fact, at the same place as esp
>> pop(tos) // -> restores  invalid value
>> 
>> The fix restores expression stack to max possible for deoptimized method size.  Please consider if this fix covers the case workarounded by  [2] (I was not able to trace back and find the reason for this changeset). 
>> 
>> [1] http://cr.openjdk.java.net/~snazarki/earlyret_crash/
>> [2] http://hg.openjdk.java.net/aarch64-port/jdk8u60/hotspot/file/83f5fdfd56ec/src/cpu/aarch64/vm/templateInterpreter_aarch64.cpp#l1909
> I don't quite understand this.  If we are the top frame, then we must
> allow space for max_stack, but in that case temps + extra_args is equal
> to max_stack anyway, so we don't need to add max_stack to extra_args.
> If we aren't the top frame, we peel back the native SP at the point of
> call.
> 
> Can you tell me a bit more about this?
> 
> Andrew.
> 
> 
> 
> -- 
> Andrew Haley
> Java Platform Lead Engineer
> Red Hat UK Ltd. <https://www.redhat.com>
> EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671