(RFR)(S)(10): 8176768: hotspot ignores PTHREAD_STACK_MIN when creating new threads (original) (raw)

Thomas Stüfe thomas.stuefe at gmail.com
Thu Mar 16 08:30:38 UTC 2017

Hi Chris, David,

the change looks good.

I see that in the launcher we require a minimum stack size across all platforms ("STACK_SIZE_MINIMUM"), should we do the same fix (adjust for PTHREAD_STACK_MIN) there?

I do not understand, why does error checking in the hotspot have to be consistent with the launcher? What prevents us from asserting in the hotspot - or at least print a warning? Note that in the hotspot, there is already UL logging ("os", "thread") after pthread_create() in the platform files, so the least we could do is add a warning log output case ppthread_attr_setstacksize fails.

If we ever refactor this coding, could we rename the variables holding the base stack size requirement for java frames - in all its incarnations in all the os_cpu files - to be renamed to something different? It is a bit confusing to have a variable which at different times in VM life means different things (before and after the call to os::Posix::set_minimum_stack_sizes()). Or, at least, rename "set_minimum_stack_sizes" to something like "adjust_minimum_stack_sizes" which makes the intent clearer.

Kind Regards, Thomas

On Thu, Mar 16, 2017 at 7:50 AM, David Holmes <david.holmes at oracle.com> wrote:

On 16/03/2017 4:33 PM, Chris Plummer wrote:

On 3/15/17 11:18 PM, David Holmes wrote:

On 16/03/2017 4:14 PM, Chris Plummer wrote:

On 3/15/17 11:11 PM, David Holmes wrote:

On 16/03/2017 3:51 PM, Chris Plummer wrote:

On 3/15/17 10:23 PM, David Holmes wrote:

Hi Chris,

On 16/03/2017 3:03 PM, Chris Plummer wrote:

Hello,

Please review the following: https://bugs.openjdk.java.net/browse/JDK-8176768 http://cr.openjdk.java.net/~cjplummer/8176768/webrev.00/webr ev.hotspot

Change looks good. While working on 8175342 I noticed our stack size on xgene was 8mb even though I was specifying -Xss72k. It turns out the following code was failing: pthreadattrsetstacksize(&attr, stacksize); So these really should be checking return values, at least in debug builds. But we can leave that until we refactor the thread startup code into osposix.cpp. I considered adding checks. I wasn't sure if we should abort or just print a warning if it failed. When we check pthread lib routines we use: int status = pthreadmutexlock(mutex); assertstatus(status == 0, status, "mutexlock"); This is for things that should only fail if we have a programming error. Ok, but this is in the launcher, so I'll need to just use the built-in assert(). I'll add that if want. Oops! I was forgetting that. Need to be consistent with launcher error checking or lack thereof. And ignore refactoring comments - not relevant. So don't add the error check? Given there is no error checking, or assertions, in those files I reluctantly have to say leave it out. Thanks, David ----- David Chris What refactoring is planned? "Planned" might be a bit strong :) I was thinking of a number of osposix related cleanups for which issues exist, but also forgot that some of our general clean-up RFE's have been closed as WNF :( I may do some of them after hours anyway :) David ----- Chris Thanks, David ----- Although we computed a minimum stack size of 72k, so -Xss72k should be fine, pthreads on this platform requires the stack be at least 128k, so it failed the pthreadattrsetstacksize() call. The end result is pthreadattrsetstacksize() had no impact on the thread's stack size, and we ended up with the platform default of 8mb. The fix is to round up the following variables to PTHREADSTACKMIN after computing their new values: javathreadminstackallowed compilerthreadminstackallowed vminternalthreadminstackallowed For solaris, there was an issue using PTHREADSTACKMIN. You need to #define POSIXCSOURCE >= 199506L in order to get PTHREADSTACKMIN #defined, and this needs to be done before including OS header files. I noticed that on solaris we were using thrminstack() elsewhere instead of PTHREADSTACKMIN, so I decided to do the same with this fix. Either way is ugly (the #define or using thrminstack()). And speaking of the existing use of thrminstack(), I deleted it. It was being applied before any adjustments to the stack sizes had been made (rounding and adding red, yellow, and shadow zones). This mean the stack ended up being larger than necessary. With the above fix in place, we are now applying thrminstack() after recomputing the minimum stack sizes. If for any reason one of those stack sizes is now too small, the correct fix is to adjust the initial stack sizes, not apply thrminstack() to the initial stack sizes. However, it looks like no adjustment is needed. I did something close to our nightly testing on all affect platforms, and no new problems turned up. thanks, Chris

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