RFR (S): [9+8u] Stack overflow in choose_collection_set on high region count

[Roman Kennke]

Looks OK.

Does it hurt to alloc once with max-regions in constructor, and dealloc in destructor?

RomanAm 03.03.2017 6:31 nachm. schrieb Aleksey Shipilev <shade at redhat.com>:
>
> Hi, 
>
> Again, running on large machine with lots of regions, you will see this: 
>
> #  SIGSEGV (0xb) at pc=0x00007f3d9ff76235, pid=26678, tid=26928 
> # 
> # JRE version: OpenJDK Runtime Environment (9.0) (fastdebug build 
> 9-internal+0-adhoc.root.shenandoah-jdk9) 
> # Java VM: OpenJDK 64-Bit Server VM (fastdebug 
> 9-internal+0-adhoc.root.shenandoah-jdk9, mixed mode, tiered, Shenandoah gc, 
> linux-amd64) 
> # Problematic frame: 
> # V  [libjvm.so+0x140c235] 
> ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet*, int*)+0x145 
>
> This is because "candidates" array in choose_collection_set is automatically 
> allocated on stack, and for large number of regions, it overflows! At best, we 
> will crash with SEGV, but may also silently corrupt something. My fault for not 
> allocating it on heap from the start. 
>
> Fix: 
>   http://cr.openjdk.java.net/~shade/shenandoah/cset-stackoverflow/webrev.01/ 
>
> Going to push to both 9 and 8u. 
>
> Testing: hotspot_gc_shenandoah (9/8u) + failing configuration on large machine 
>
>
> Thanks, 
> -Aleksey 
>