RFR: 8271490: [ppc] [s390]: Crash in JavaThread::pd_get_top_frame_for_profiling

[Thomas Stuefe]

On Tue, 10 Aug 2021 14:50:34 GMT, Lutz Schmidt <lucy at openjdk.org> wrote:

> Please review this pull request. It hardens the code on ppc and s390 against crashes while collecting stack traces for JFR. Stack frame collection in prims/forte.cpp will benefit from this fix as well as it uses the same platform-specific code.
> 
> Testing:
> SAP-internal functional and stress testing. Verifying a positive effect is hard because the targeted crashes occur only very rarely. No negative side effects of the fix have been observed.

LGTM. Minor comment nits.

src/hotspot/os_cpu/linux_s390/thread_linux_s390.cpp line 97:

> 95:       //  - ijava_state_unchecked() calculates it's result as
> 96:       //      istate = fp() - z_ijava_state_size() = NULL - 0x68 DEBUG_ONLY(-8)
> 97:       //  - istate->method dereferences memory at offset 8 from istate

I think a reference to the JBS issue would suffice as a comment here.

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Marked as reviewed by stuefe (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/5071