Review request 6983240: guarantee((Solaris::min_stack_allowed >= (StackYellowPages+StackRedPages...) wrong
coleen.phillimore at oracle.com
Tue Oct 5 08:26:24 PDT 2010
Thanks David - some comments inline...
On 10/04/10 20:41, David Holmes wrote:
> Hi Coleen,
> In os_solaris.cpp this comment should now refer to 2*BytesPerWord
> // Add in BytesPerWord times page size to account for VM stack during
> // class initialization depending on 32 or 64 bit VM.
> That said this formulation (not your I know) is confusing. What does
> bytesPerWord have to do with the amount of stack needed? Is this just
> some weird way of getting twice the amount of stack on 64-bit as
> 32-bit? Are the pages sizes even the same in that case?
Yeah, I believe it's just to account for 64 vs. 32 bit. The page sizes
are the same if 32 or 64 bit. I have
> Also in os_solaris.cpp isn't this guarantee always false:
> ! guarantee(os::Solaris::min_stack_allowed >= thr_min_stack(),
> ! "need to increase min_stack_allowed");
No, it doesn't assert, because in your next mail you found that
thr_min_stack() is smaller than our min_stack_allowed. I could revert
that change but min_stack_allowed() is for the VM to get initialized
rather than this thr_min_stack() which is for the OS to initialize the
thread. I would assume the latter is always smaller than the former or
something is really wrong. Changing it back probably doesn't hurt anything.
> AFAICS min_stack_allowed is set to one of these values:
> os::Solaris::min_stack_allowed = 128*K;
> os::Solaris::min_stack_allowed = 96*K;
> os::Solaris::min_stack_allowed = 224*K;
> os::Solaris::min_stack_allowed = 64*K;
> but the manpage for thr_min_stack states:
> thr_min_stack() will return the unsigned int THR_MIN_STACK,
> which is the minimum-allowable size for a thread's stack.
> In this implementation the default size for a user-thread's
> stack is one mega-byte.
> 1MB > all the above. ???
> Coleen Phillimore said the following on 10/05/10 08:45:
>> Summary: min_stack_allowed is a compile time constant and Stack*Pages
>> are settable
>> Also stress tested various combinations of -Xss and
>> -XX:StackShadowPages=n. This also fixes a bug
>> 6346701: stack overflow in native method results in segfault, not a
>> or rather it fixes the observed SEGVs with different settings of -Xss
>> and -XX:StackShadowPages in the evaluation. We were getting stack
>> overflow before the stack overflow exception was initialized, causing
>> infinite recusion trying to initialize it.
>> Also fixed a random g++ compilation error.
>> open webrev at http://cr.openjdk.java.net/~coleenp/6983240/
>> bug link at http://bugs.sun.com/view_bug.do?bug_id=6983240
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