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tools/llvm-exegesis/X86/latency tests fail with glibc 2.40 #100791

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mgorny opened this issue Jul 26, 2024 · 4 comments · Fixed by #100804
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tools/llvm-exegesis/X86/latency tests fail with glibc 2.40 #100791

mgorny opened this issue Jul 26, 2024 · 4 comments · Fixed by #100804
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tools:llvm-exegesis
Milestone
LLVM 19.X Release

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@mgorny
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mgorny commented Jul 26, 2024

After upgrading the system to glibc 2.40, the following tests started failing:

Failed Tests (8):
  LLVM :: tools/llvm-exegesis/X86/latency/memory-annotations-livein.s
  LLVM :: tools/llvm-exegesis/X86/latency/memory-annotations.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess-abnormal-exit-code.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess-address-annotation.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess-rsp.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess-segfault.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess.s

FWICS, in all instances the failure has the same cause:

RUN: at line 3: /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm_build-abi_x86_64.amd64/bin/llvm-exegesis -mtriple=x86_64-unknown-unknown -mode=latency -snippets-file=/var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s -execution-mode=subprocess | /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm_build-abi_x86_64.amd64/bin/FileCheck /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s
+ /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm_build-abi_x86_64.amd64/bin/FileCheck /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s
+ /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm_build-abi_x86_64.amd64/bin/llvm-exegesis -mtriple=x86_64-unknown-unknown -mode=latency -snippets-file=/var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s -execution-mode=subprocess
llvm-exegesis error: Child benchmarking process exited with non-zero exit code: Disabling restartable sequences failed
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm_build-abi_x86_64.amd64/bin/FileCheck /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s
@mgorny mgorny added this to the LLVM 19.X Release milestone Jul 26, 2024
@github-project-automation github-project-automation bot moved this to Needs Triage in LLVM Release Status Jul 26, 2024
@llvmbot
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llvmbot commented Jul 26, 2024

@llvm/issue-subscribers-tools-llvm-exegesis

Author: Michał Górny (mgorny)

After upgrading the system to glibc 2.40, the following tests started failing: 
Failed Tests (8):
  LLVM :: tools/llvm-exegesis/X86/latency/memory-annotations-livein.s
  LLVM :: tools/llvm-exegesis/X86/latency/memory-annotations.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess-abnormal-exit-code.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess-address-annotation.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess-rsp.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess-segfault.s
  LLVM :: tools/llvm-exegesis/X86/latency/subprocess.s

FWICS, in all instances the failure has the same cause:

RUN: at line 3: /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm_build-abi_x86_64.amd64/bin/llvm-exegesis -mtriple=x86_64-unknown-unknown -mode=latency -snippets-file=/var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s -execution-mode=subprocess | /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm_build-abi_x86_64.amd64/bin/FileCheck /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s
+ /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm_build-abi_x86_64.amd64/bin/FileCheck /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s
+ /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm_build-abi_x86_64.amd64/bin/llvm-exegesis -mtriple=x86_64-unknown-unknown -mode=latency -snippets-file=/var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s -execution-mode=subprocess
llvm-exegesis error: Child benchmarking process exited with non-zero exit code: Disabling restartable sequences failed
FileCheck error: '&lt;stdin&gt;' is empty.
FileCheck command line:  /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm_build-abi_x86_64.amd64/bin/FileCheck /var/tmp/portage/sys-devel/llvm-19.1.0_rc1/work/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-preserved-registers.s

@boomanaiden154
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Do you know if this fails with glibc 2.39?

__rseq_size now denotes the size of the active rseq area (20 bytes initially), not the size of struct rseq (32 bytes initially).

This section from the glibc v2.40 release notes looks suspicous.

@mgorny
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mgorny commented Jul 26, 2024

Do you know if this fails with glibc 2.39?

I'm reasonably convinced it doesn't. The previous version I've tested (prior to glibc upgrade) was 72d8c27, and it didn't have any issues. I can retest that commit later, if you wish, but I want to finish with rc1 first, as otherwise I'll probably lose ccache :-).

@boomanaiden154
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It's definitely that 2.40 glibc change causing the breakage. The kernel checks that the size in the unregister call matches the size of the currently registered rseq struct https://github.com/torvalds/linux/blob/2f8c4f5062855a83c1f2dbc012c4fa274ce999d4/kernel/rseq.c#L376

The patch that adjusted this was https://patchwork.sourceware.org/project/glibc/patch/[email protected]/#177251.

Looks like I need to figure out if glibc still publicly exposes the actual size of the struct.

boomanaiden154 added a commit to boomanaiden154/llvm-project that referenced this issue Jul 26, 2024
@boomanaiden154
[llvm-exegesis] Use correct rseq struct size
eee2860 
Glibc v2.40 changes the definition of __rseq_size to the usable area of
the struct rather than the actual size of the struct to accommodate
users trying to figure out what features can be used. This change breaks
llvm-exegesis trying to disable rseq as the size registered in the
kernel is no longer equal to __rseq_size. This patch adds a check to see
if __rseq_size is less than 32 bytes and uses 32 as a value if it is
given alignment requirements.

Fixes llvm#100791.
boomanaiden154 added a commit to boomanaiden154/llvm-project that referenced this issue Jul 26, 2024
@boomanaiden154
[llvm-exegesis] Use correct rseq struct size
84837e3 
Glibc v2.40 changes the definition of __rseq_size to the usable area of
the struct rather than the actual size of the struct to accommodate
users trying to figure out what features can be used. This change breaks
llvm-exegesis trying to disable rseq as the size registered in the
kernel is no longer equal to __rseq_size. This patch adds a check to see
if __rseq_size is less than 32 bytes and uses 32 as a value if it is
given alignment requirements.

Fixes llvm#100791.
@boomanaiden154 boomanaiden154 mentioned this issue Jul 26, 2024
Merged
@github-project-automation github-project-automation bot moved this from Needs Triage to Done in LLVM Release Status Jul 27, 2024
llvmbot pushed a commit to llvmbot/llvm-project that referenced this issue Jul 27, 2024
@boomanaiden154 @llvmbot
[llvm-exegesis] Use correct rseq struct size (llvm#100804)
9103e65 
Glibc v2.40 changes the definition of __rseq_size to the usable area of
the struct rather than the actual size of the struct to accommodate
users trying to figure out what features can be used. This change breaks
llvm-exegesis trying to disable rseq as the size registered in the
kernel is no longer equal to __rseq_size. This patch adds a check to see
if __rseq_size is less than 32 bytes and uses 32 as a value if it is
given alignment requirements.

Fixes llvm#100791.

(cherry picked from commit 1e8df9e)
llvmbot pushed a commit to llvmbot/llvm-project that referenced this issue Jul 27, 2024
@boomanaiden154 @llvmbot
[llvm-exegesis] Use correct rseq struct size (llvm#100804)
ba53532 
Glibc v2.40 changes the definition of __rseq_size to the usable area of
the struct rather than the actual size of the struct to accommodate
users trying to figure out what features can be used. This change breaks
llvm-exegesis trying to disable rseq as the size registered in the
kernel is no longer equal to __rseq_size. This patch adds a check to see
if __rseq_size is less than 32 bytes and uses 32 as a value if it is
given alignment requirements.

Fixes llvm#100791.

(cherry picked from commit 1e8df9e)
tru pushed a commit to llvmbot/llvm-project that referenced this issue Jul 29, 2024
@boomanaiden154 @tru
[llvm-exegesis] Use correct rseq struct size (llvm#100804)
cbfbbd7 
Glibc v2.40 changes the definition of __rseq_size to the usable area of
the struct rather than the actual size of the struct to accommodate
users trying to figure out what features can be used. This change breaks
llvm-exegesis trying to disable rseq as the size registered in the
kernel is no longer equal to __rseq_size. This patch adds a check to see
if __rseq_size is less than 32 bytes and uses 32 as a value if it is
given alignment requirements.

Fixes llvm#100791.

(cherry picked from commit 1e8df9e)
@SomeoneSerge SomeoneSerge mentioned this issue Oct 16, 2024
Merged
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[llvm-exegesis] Use correct rseq struct size boomanaiden154/llvm-project
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@mgorny @boomanaiden154 @llvmbot