On Thu, 20 Aug 2026 08:40:46 GMT, Ashay Rane <[email protected]> wrote:
>> Prior to this patch, the `StackYellowPages` and `StackRedPages` >> influenced the total reserved stack memory, but they didn't change the >> minimum stack size specified as required by HotSpot to Windows. This >> patch adds the call to `SetThreadStackGuarantee()` to set the minimum >> stack size. >> >> The key change here is that the argument to `SetThreadStackGuarantee()` >> is set to one less than the total number of yellow pages. The one less >> page is because Windows uses a guard page (access to which tells Windows >> to commit more stack pages); in the terminal case, we want the guard >> page to coincide with the top-most yellow stack page, thus leaving all >> except one yellow page available as the stack size. >> >> Importantly, however, we do not use the red page count as the argument >> to `SetThreadStackGurantee()`, since the red stack pages are unavailable >> for handling recoverable overflows. The red page count impacts the >> _total reserved_ stack size, just not the _minimum_ stack size. Still, >> forcing the red stack page count to be included into the computation of >> the argument to `SetThreadStackGurantee()` causes HotSpot to fail with >> the assertion `assert(!in_vm) failed: Undersized StackShadowPages`, >> since Windows is unable to commit more stack pages due to the minimum >> stack size now being larger than just the yellow page count minus one. >> >> The accompanying test passes zero to `SetThreadStackGuarantee()` to >> probe the current minimum stack size, which we then compare against the >> expected size based on the yellow page count. The same test fails >> without this patch on both Windows/x64 and on Windows/ARM64. >> >> Validated this patch by running through all tier 1, 2, and 3 HotSpot >> jtreg tests on Windows/x64 and Windows/ARM64 in FastDebug config. >> >> --------- >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). > > Ashay Rane has updated the pull request incrementally with one additional > commit since the last revision: > > Update comment block to be precise about `SetThreadStackGuarantee()` If we need to add +1 to DEFAULT_STACK_YELLOW_PAGES on Windows for all CPUs, can't we just move the +1 to pd_create_stack_guard_pages(), which would cancel out the "- os::vm_page_size()"? It seems to be an accounting issue +/- 1 for the guard page, but we can choose where to do the adjustment. Or another way to look at it is, do we have a precise meaning for yellow pages, and whether they include or exclude the guard page? Either way, DEFAULT_STACK_YELLOW_PAGES should be treated the same for x86 and aarch64, right? Regarding SetThreadStackGuarantee, I thought we need it so that Windows triggers EXCEPTION_STACK_OVERFLOW in the right place. If Y and G are out of sync, does EXCEPTION_STACK_OVERFLOW happen at the right place? ------------- PR Comment: https://git.openjdk.org/jdk/pull/32365#issuecomment-5363037768
