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8296136: Use correct register in aarch64_enc_fast_unlock() #10921

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@rkennke rkennke commented Oct 31, 2022

In aarch64_enc_fast_unlock() (aarch64.ad) we have this piece of code:

    __ ldr(tmp, Address(oop, oopDesc::mark_offset_in_bytes()));
    __ tbnz(disp_hdr, exact_log2(markWord::monitor_value), object_has_monitor);

The tbnz uses the wrong register - it should really use tmp. disp_hdr has been loaded with the displaced header of the stack-lock, which would never have its monitor bits set, thus the branch will always take the slow path. In this common case, it is only a performance nuisance. In the case of !UseHeavyMonitors it is even worse, then disp_hdr will be unitialized, and we are facing a correctness problem.

As far as I can tell, the problem dates back to when aarch64 C2 parts have been added to OpenJDK.

Testing:

  • tier1
  • tier2
  • tier3
  • tier4

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  • JDK-8296136: Use correct register in aarch64_enc_fast_unlock()

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk pull/10921/head:pull/10921
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Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk pull/10921/head

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$ git pr checkout 10921

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Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/10921.diff

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bridgekeeper bot commented Oct 31, 2022

👋 Welcome back rkennke! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

@openjdk openjdk bot added the rfr Pull request is ready for review label Oct 31, 2022
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@rkennke The following label will be automatically applied to this pull request:

  • hotspot-compiler

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

@openjdk openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Oct 31, 2022
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mlbridge bot commented Oct 31, 2022

Webrevs

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Ouch!

Yes, thanks. I just checked the code against x86, which confirms your analysis.

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openjdk bot commented Oct 31, 2022

@rkennke This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8296136: Use correct register in aarch64_enc_fast_unlock()

Reviewed-by: aph, fyang

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 4 new commits pushed to the master branch:

  • 37107fc: 8296007: crash in runtime/DefineClass/NullClassBytesTest.java
  • 4999f2c: 8156593: DataOutput.write(byte[],int,int) and its implementations do not specify index out bounds
  • 8480f87: 8291974: PrivateCredentialPermission should not use local variable to enable debugging
  • 590de37: 8284842: Update Unicode Data Files to Version 15.0.0

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

@openjdk openjdk bot added the ready Pull request is ready to be integrated label Oct 31, 2022
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RealFYang commented Nov 1, 2022

Could you please also incorporate following fix for RISC-V at the same time? I see it inherits the same similar issue here.
This has passed tier1 test on HiFive Unmatched board. Thanks.

diff --git a/src/hotspot/cpu/riscv/riscv.ad b/src/hotspot/cpu/riscv/riscv.ad
index 75612ef7508..abe0f609a62 100644
--- a/src/hotspot/cpu/riscv/riscv.ad
+++ b/src/hotspot/cpu/riscv/riscv.ad
@@ -2474,7 +2474,7 @@ encode %{

     // Handle existing monitor.
     __ ld(tmp, Address(oop, oopDesc::mark_offset_in_bytes()));
-    __ andi(t0, disp_hdr, markWord::monitor_value);
+    __ andi(t0, tmp, markWord::monitor_value);
     __ bnez(t0, object_has_monitor);

     if (!UseHeavyMonitors) {

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rkennke commented Nov 1, 2022

Could you please also incorporate following fix for RISC-V at the same time? I see it inherits the same similar issue here. This has passed tier1 test on HiFive Unmatched board. Thanks.

diff --git a/src/hotspot/cpu/riscv/riscv.ad b/src/hotspot/cpu/riscv/riscv.ad
index 75612ef7508..abe0f609a62 100644
--- a/src/hotspot/cpu/riscv/riscv.ad
+++ b/src/hotspot/cpu/riscv/riscv.ad
@@ -2474,7 +2474,7 @@ encode %{

     // Handle existing monitor.
     __ ld(tmp, Address(oop, oopDesc::mark_offset_in_bytes()));
-    __ andi(t0, disp_hdr, markWord::monitor_value);
+    __ andi(t0, tmp, markWord::monitor_value);
     __ bnez(t0, object_has_monitor);

     if (!UseHeavyMonitors) {

I pushed the proposed fix for RISC-V. Could you please give it a quick build and smoke test, and approve the PR? Then I'd integrate it. Thanks!

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RealFYang commented Nov 1, 2022

Could you please also incorporate following fix for RISC-V at the same time? I see it inherits the same similar issue here. This has passed tier1 test on HiFive Unmatched board. Thanks.

diff --git a/src/hotspot/cpu/riscv/riscv.ad b/src/hotspot/cpu/riscv/riscv.ad
index 75612ef7508..abe0f609a62 100644
--- a/src/hotspot/cpu/riscv/riscv.ad
+++ b/src/hotspot/cpu/riscv/riscv.ad
@@ -2474,7 +2474,7 @@ encode %{

     // Handle existing monitor.
     __ ld(tmp, Address(oop, oopDesc::mark_offset_in_bytes()));
-    __ andi(t0, disp_hdr, markWord::monitor_value);
+    __ andi(t0, tmp, markWord::monitor_value);
     __ bnez(t0, object_has_monitor);

     if (!UseHeavyMonitors) {

I pushed the proposed fix for RISC-V. Could you please give it a quick build and smoke test, and approve the PR? Then I'd integrate it. Thanks!

Yes, my local tests looks good. I think we are ready to go. Thanks again.

PS: I ran tier1-tier3 tests and other non-trivial benchmark workloads like Renaissance, Dacapo, Specjbb2015, etc.

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rkennke commented Nov 2, 2022

Thank you!

/integrate

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openjdk bot commented Nov 2, 2022

Going to push as commit 7619602.
Since your change was applied there have been 15 commits pushed to the master branch:

  • 47d513b: 8252075: Documentation error in LayoutManager2 interface
  • 8de3eda: 8295476: Split G1 cost per byte predictor on gc phase
  • 2634eff: 8295646: Ignore zero pairs in address descriptors read by dwarf parser
  • 50d91a3: 8057113: (fs) Path should have a method to obtain the filename extension
  • d17bf51: 8295914: Add a header to generated HTML files in specs
  • 9911405: 8282958: Rendering issues of borders, TextFields on Windows High-DPI systems
  • 2fb64a4: 8296162: [aarch64] Remove unused Address::_is_lval
  • 15b8b45: 8296161: [aarch64] Remove unused "pcrel" addressing mode tag
  • f829b5a: 8280378: [IR Framework] Support IR matching for different compile phases
  • da0ae51: 8296167: test/langtools/tools/jdeps/jdkinternals/ShowReplacement.java failing after JDK-8296072
  • ... and 5 more: https://git.openjdk.org/jdk/compare/16744b34498e7aac59caef8c9b1a3d4d15f8c22e...master

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated Pull request has been integrated label Nov 2, 2022
@openjdk openjdk bot closed this Nov 2, 2022
@openjdk openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Nov 2, 2022
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openjdk bot commented Nov 2, 2022

@rkennke Pushed as commit 7619602.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

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