RFR(S): 8186293: [aix] Fix thread creation with huge stack sizes

[Thomas Stüfe]

Hi Goetz,

thanks for this fix! Some small nits:

"+ // On linux, pthread_attr_setstacksize succeeds with huge values, but
+  // pthread_create() fails.

No need to mention Linux here.

+   On Aix, this fails and leaves the minimal system
+  // thread size in attr."

We do not know this :) We only know it leaves the pthread_attr structure
untouched. It was filled by pthread_attr_init() with default values. Stack
default size may be minimally possible size, but I rather doubt this.

How about instead: "On Aix, this fails and leaves the pthread_attr
structure untouched"

-  pthread_attr_setguardsize(&attr, os::Aix::default_guard_size(thr_type));
+    ret = pthread_attr_setguardsize(&attr,
os::Aix::default_guard_size(thr_type));

I would not bother checking the setting of the guard page. The only reason
it makes even sense to set the guard page size is for java threads, where
we set it to zero because we do not want to spend memory for a system guard
page if we have our own guard pages. See os::Aix::default_guard_size. For
all other threads, this is supposed to be one page. But as a stack page may
be 4 or 64k, this is flaky and may fail.

In fact, thinking about this, I think a better way to do this would to be
to call pthread_attr_setguardsize() only to disable system guard pages, and
to otherwise live with the system guard page default.

--

The rest is fine. I leave it up to you if you take my proposals. Do not
need another webrev.

..Thomas



On Wed, Aug 16, 2017 at 4:24 PM, Lindenmaier, Goetz <
goetz.lindenmaier at sap.com> wrote:

> Hi,
>
> TestOptionWithRanges causes the vm on aix to crash on some machines.
> This is because huge stack sizes are not treated properly.
>
> On linux, pthread_attr_setstacksize succeeds if called with huge values,
> but
> pthread_create() then fails. On Aix, pthread_attr_setstacksize  fails if
> passed a value exceeding the limits and leaves the minimal system
> thread stack size in attr. Thus thread creation succeeds and leads to
> crashes after thread creation when the guard pages shall be protected
> but don't fit on the tiny stack created.
>
> Please review this small, aix-only change.
> http://cr.openjdk.java.net/~goetz/wr17/8186293-aixHugeStack/webrev.01/
>
> Best regards,
>   Goetz.
>