Integrated: 8253464: ARM32 Zero: atomic_copy64 is incorrect, breaking volatile stores
Aleksey Shipilev
shade at openjdk.java.net
Wed Sep 23 16:55:37 UTC 2020
On Tue, 22 Sep 2020 14:12:42 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:
> There is a regression introduced by addition of ARMv7-specific block by JDK-8211387. It readily manifests as crash
> during jcstress initialization, and investigation points at broken volatile stores. Reverting JDK-8211387 from head JDK
> makes ARM32 start and run jcstress. The underlying reason seems to be the half-done `atomic_copy64`: it does the load
> with exclusive load, but then defers to the C++ store. Somewhere during handing over the value from the asm load to C++
> store and/or C++ store itself, we garble the value. The way out is to implement the whole thing in asm. Also see
> `StubGenerator::generate_atomic_load_long` and `StubGenerator::generate_atomic_store_long` in `stubGenerator_arm.cpp`,
> that do roughly the same thing and were the basis for this implementation. Attention @theRealAph, @bulasevich.
>
> Testing:
> - [x] ARM32 Linux zero release jcstress run
This pull request has now been integrated.
Changeset: c21690b5
Author: Aleksey Shipilev <shade at openjdk.org>
URL: https://git.openjdk.java.net/jdk/commit/c21690b5
Stats: 17 lines in 1 file changed: 8 ins; 0 del; 9 mod
8253464: ARM32 Zero: atomic_copy64 is incorrect, breaking volatile stores
Reviewed-by: aph
-------------
PR: https://git.openjdk.java.net/jdk/pull/299
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