RFR: 8236569: -Xss not multiple of 4K does not work for the main thread on macOS

[Vladimir Kempik]

On Sun, 30 May 2021 03:00:56 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> …d on macOS
>> 
>> This patch simply round up the specified stack size to multiple of the system page size. 
>> 
>> Test is trivial, simply run java with -Xss option against following code. On MacOS, before the fix, running with `-Xss159k` and `-Xss160k` would get `7183` and `649` respectively. After fix, both would output `649`, while `-Xss161k` would be same as `-Xss164k` and see 691 as the output.
>> 
>> ```code:java
>> public class StackLeak {
>>     public int depth = 0;
>>     public void stackLeak() {
>>         depth++;
>>         stackLeak();
>>     }
>> 
>>     public static void main(String[] args) {
>>         var test = new StackLeak();
>>         try {
>>             test.stackLeak();
>>         } catch (Throwable e) {
>>             System.out.println(test.depth);
>>         }
>>     }
>> }
>
> src/java.base/macosx/native/libjli/java_md_macosx.m line 727:
> 
>> 725: 
>> 726: static size_t alignUp(size_t stack_size) {
>> 727:     long page_size = sysconf(_SC_PAGESIZE);
> 
> In hotspot we use `getpagesize()`. There is also a guard for a very large stack (within a page of SIZE_MAX) so that rounding up does not produce zero.

sounds like that (getpagesize) should work with m1 mac as well, as they have 16k pages. will it ?

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PR: https://git.openjdk.java.net/jdk/pull/4256