Request for review: 6761744 Hotspot crashes if process size limit is exceeded

[Bengt Rutisson]

Hi Tao,

I agree with John. The changes look fine and I'm ok with them. But it 
would look nicer to add the CollectedHeap::add_and_verify_no_overflow() 
method.

Also, regarding the test, a couple of minor things.

First, with the new naming convention I think the test should be called 
something like:

test/gc/init/TestHandleExceedingProcessSizeLimitOn32BitSystems.java

Then I think you can reduce the code duplication a bit. You create the 
same ProcessBuilder and OutputAnalyzer in both 32 and 64 bit cases. So 
maybe it could look like this instead:

public class TestHandleExceedingProcessSizeLimitOn32BitSystems {
   public static void main(String args[]) throws Exception {
     ProcessBuilder pb =
ProcessTools.createJavaProcessBuilder(System.getProperty("test.vm.opts"),
"-Xmx3072m",
"-XX:MaxPermSize=1024m",
"-version");
     OutputAnalyzer output = new OutputAnalyzer(pb.start());

     String dataModel = System.getProperty("sun.arch.data.model");
     if (dataModel.equals("32")) {
       output.shouldContain("The size of the object heap + perm gen 
exceeds the maximum representable size");
       if (output.getExitValue() == 0) {
         throw new RuntimeException("Not expected to get exit value 0");
       }
     } else if (dataModel.equals("64")) {
       output.shouldHaveExitValue(0);
     }
   }
}

There is also a small bug in the test. If you run JTreg without passing 
any vmoptions the test will fail. The reason is that 
System.getProperty("test.vm.opts") will evaluate to the empty string. 
This will be passed as the first argument to the Java process, which 
will assume that this is the class name. So, it fails to start because 
it can't load the class <empty string>.

To reproduce the problem use this command line:

java  -jar <path_to_jtreg>/lib/jtreg.jar 
test/gc/6761744/TestHandleExceedingProcessSizeLimitOn32BitSystems.java

I guess the fix is to check that System.getProperty("test.vm.opts") is 
not empty before passing it on to createJavaProcessBuilder().

Thanks,
Bengt

On 4/13/13 3:15 AM, John Cuthbertson wrote:
> Hi Tao,
>
> This looks OK to me.
>
> I can see what Thomas is saying though. All of the checks involve 
> something like:
>
> total += some_value;
> if (total < some_value) {
>   // We must have overflowed
>   vm_exit(...);
> }
>
> So a function in CollectedHeap (the base class of SharedHeap and 
> ParallelScavengeHeap) might make sense. For example:
>
> total_reserved = 0;
> total_reserved = add_and_verify_no_overflow(total_reserved, 
> max_heap_size);
> total_reserved = add_and_verify_no_overflow(total_reserved, 
> max_perm_size);
>
> Where the function is:
>
> size_t add_and_verify_no_overflow(size_t x, size_t y) {
>   const char* msg = "...";
>   x += y;
>   if (x < y) {
>     vm_exit(msg);
>   }
>   return x;
> }
>
> But I can live with your current changes.
>
> JohnC
>
> On 4/10/2013 9:52 AM, Tao Mao wrote:
>> Hi Bengt,
>>
>> Thank you for reviewing. A new webrev is updated.
>> http://cr.openjdk.java.net/~tamao/6761744/webrev.01/
>>
>> Cheers,
>> Tao
>>
>> On 4/10/13 1:54 AM, Bengt Rutisson wrote:
>>>
>>> Hi Tao,
>>>
>>> This change looks good. Thanks for adding the JTReg test, it looks good!
>>>
>>> One minor nit:
>>>
>>> In src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp I would 
>>> suggest to store "(size_t) align_size_up(pgs->max_size(), 
>>> HeapRegion::GrainBytes)" in a local variable rather than duplicating 
>>> the calculation.
>>>
>>> Thanks,
>>> Bengt
>>>
>>> On 4/8/13 7:22 AM, Tao Mao wrote:
>>>> 6761744 Hotspot crashes if process size limit is exceeded
>>>> https://jbs.oracle.com/bugs/browse/JDK-6761744
>>>>
>>>> webrev:
>>>> http://cr.openjdk.java.net/~tamao/6761744/webrev.00/
>>>>
>>>> changeset:
>>>> The fix only needs to go to hsx24 since there's no perm gen in 
>>>> hotspot-25. Thus, the webrev is based on hsx24 repo.
>>>>
>>>> It provides for 32-bit builds a preventive check of the size of 
>>>> "the object heap + perm gen" before reserving VM memory. The total 
>>>> size should not exceed 4096MB (i.e. 4GB) for 32-bit builds; 
>>>> otherwise, the total doesn't make sense and, what's worse, overflow 
>>>> occurs. It will consequentially trigger anther error of memory 
>>>> access violation, which was not protected.
>>>>
>>>> jtreg testing java code is also written, checking both 32-bit and 
>>>> (trivially) 64-bit builds.
>>>>
>>>> testing:
>>>> check jtreg tests with flags -XX:+UseParallelGC, -XX:+UseG1GC, 
>>>> -XX:+UseParNewGC, -XX:+UseConcMarkSweepGC, -XX:+UseSerialGC and 
>>>> builds of 32-bit and 64-bit. All passed.
>>>>
>>>> Needs JPRT test when pushing.
>>>
>

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