On Mon, 28 Sep 2026 00:48:39 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: > > Handle EXCEPTION_STACK_OVERFLOW when yellow zone is unguarded > > The previous code did not handle a corner case that arises when HotSpot > receives `EXCEPTION_STACK_OVERFLOW` (since the guard page cannot be > moved further down) while already processing a recoverable overflow. In > this case, the yellow and reserved zones are writable (as part of the > recoverable overflow), so we retry the same instruction. If the > faulting probe reaches the red zone, we'll receive > `EXCEPTION_ACCESS_VIOLATION`, which will be handled as an unrecoverable > overflow. Dean, something that I learnt (and which was a surprise to me) perhaps could be useful to you too; that the pages that we request to be set aside using `SetThreadStackGuarantee()` aren't pinned to the bottom of the stack. On the contrary, since these pages are located just after the committed stack pages, these stack guarantee pages move as new stack pages get committed. So as far as I can tell, in the orientation where high addresses are at the top and low addresses at the bottom, there's no way to make the guaranteed zone below the yellow zone. To be precise, the guaranteed zone starts above the yellow zone. Then, as the stack becomes close to full, it approaches the yellow zone but (as far as I know) it never hops _over_ the yellow zone to then coincide with the red zone. ------------- PR Comment: https://git.openjdk.org/jdk/pull/32365#issuecomment-5945431899
