RFR 8203466: intermittent crash at jdk.internal.misc.Unsafe::getObjectVolatile (native)

[coleen.phillimore at oracle.com]

On 9/14/18 4:01 PM, dean.long at oracle.com wrote:
> Hi Coleen.  In the bug you asked:
>
> > Why can't we just push rdi and rsi to the stack and restore them? 
> This code appears to be leaf code so shouldn't care about stack format
>
> Did that ever get answered?  If there is concern about the pushes and 
> pops canceling out at the end, you could always reserve the stack 
> space at the beginning, after
>
> __ enter();
>
> and then setup_arg_regs/restore_arg_regs would not need to adjust the 
> stack pointer.

The reason I didn't do this is that I couldn't get it to work for all 
the various call sites.  Also, the barrier code is going to need the 
thread register sometimes which wasn't available.  So I went with this.  
I'm somewhat unclear with how this is called from the c2 code.  If you 
want to try this solution, I should probably give up and reassign it to 
compiler.

thanks,
coleen

>
> dl
>
> On 9/14/18 11:32 AM, coleen.phillimore at oracle.com wrote:
>> Summary: Save windows 64 callee saved registers rsi, rdi to Thread, 
>> save r15, also callee saved to r9
>>
>> This is done for generated stubs that do arraycopy that need GC 
>> barrier code because GC assumes that r10 is scratch, since it's 
>> defined as rscratch1.  See bug for more details.  Thanks Erik for 
>> your help and the diagnosis.
>>
>> Tested with mach5 hs-tier1-7.  We don't have a reproduceable test case.
>>
>> open webrev at http://cr.openjdk.java.net/~coleenp/8203466.01/webrev
>> bug link https://bugs.openjdk.java.net/browse/JDK-8203466
>>
>> Thanks,
>> Coleen
>>
>