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[PW_SID:1076232] cmpxchg: allow const-qualified old value in cmpxchg()#1705

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[PW_SID:1076232] cmpxchg: allow const-qualified old value in cmpxchg()#1705
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@linux-riscv-bot linux-riscv-bot commented Apr 2, 2026

PR for series 1076232 applied to workflow__riscv__fixes

Name: cmpxchg: allow const-qualified old value in cmpxchg()
URL: https://patchwork.kernel.org/project/linux-riscv/list/?series=1076232
Version: 1

@liuhangbin
cmpxchg: allow const-qualified old value in cmpxchg()
4de84c6 
The old value passed to cmpxchg() is semantically read-only: it is
only loaded into a register as a comparand and is never written back.
However, the macro currently assigns it implicitly to a local variable
of type __typeof__(*(ptr)), which triggers -Werror=discarded-qualifiers
when old is a const-qualified pointer and ptr points to a non-const type.

To avoid this, let's add an explicit cast to __typeof__(*(ptr)) for the
old local variable in the cmpxchg macros. This explicit cast suppresses
the -Wdiscarded-qualifiers diagnostic.

The new value is intentionally left without a cast: new will be stored
into *ptr, so silently accepting a const-qualified new would allow
callers to store a pointer-to-const into a non-const location without
any compiler warning.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>
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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
build-rv32-defconfig
Desc: Builds riscv32 defconfig
Duration: 137.51 seconds
Result: PASS

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
build-rv64-clang-allmodconfig
Desc: Builds riscv64 allmodconfig with Clang, and checks for errors and added warnings
Duration: 2162.61 seconds
Result: PASS

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
build-rv64-gcc-allmodconfig
Desc: Builds riscv64 allmodconfig with GCC, and checks for errors and added warnings
Duration: 2930.42 seconds
Result: PASS

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
build-rv64-nommu-k210-defconfig
Desc: Builds riscv64 defconfig with NOMMU for K210
Duration: 26.90 seconds
Result: PASS

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
build-rv64-nommu-k210-virt
Desc: Builds riscv64 defconfig with NOMMU for the virt platform
Duration: 32.69 seconds
Result: PASS

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
checkpatch
Desc: Runs checkpatch.pl on the patch
Duration: 4.39 seconds
Result: WARNING
Output:

WARNING: please, no spaces at the start of a line
#118: FILE: arch/powerpc/include/asm/cmpxchg.h:701:
+     __typeof__(*(ptr)) _o_ = (__typeof__(*(ptr)))(o);^I^I^I \$

WARNING: please, no spaces at the start of a line
#127: FILE: arch/powerpc/include/asm/cmpxchg.h:710:
+     __typeof__(*(ptr)) _o_ = (__typeof__(*(ptr)))(o);^I^I^I \$

WARNING: please, no spaces at the start of a line
#180: FILE: arch/sh/include/asm/cmpxchg.h:71:
+     __typeof__(*(ptr)) _o_ = (__typeof__(*(ptr)))(o);^I^I^I \$

WARNING: please, no spaces at the start of a line
#206: FILE: arch/sparc/include/asm/cmpxchg_64.h:173:
+     __typeof__(*(ptr)) _o_ = (__typeof__(*(ptr)))(o);^I^I^I \$

total: 0 errors, 4 warnings, 0 checks, 144 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
      mechanically convert to the typical style using --fix or --fix-inplace.

Commit 4de84c669397 ("cmpxchg: allow const-qualified old value in cmpxchg()") has style problems, please review.

NOTE: Ignored message types: ALLOC_SIZEOF_STRUCT CAMELCASE COMMIT_LOG_LONG_LINE GIT_COMMIT_ID MACRO_ARG_REUSE NO_AUTHOR_SIGN_OFF

NOTE: If any of the errors are false positives, please report
      them to the maintainer, see CHECKPATCH in MAINTAINERS.
total: 0 errors, 4 warnings, 0 checks, 144 lines checked
WARNING: please, no spaces at the start of a line

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
dtb-warn-rv64
Desc: Checks for Device Tree warnings/errors
Duration: 84.24 seconds
Result: PASS

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
header-inline
Desc: Detects static functions without inline keyword in header files
Duration: 0.26 seconds
Result: PASS

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
kdoc
Desc: Detects for kdoc errors
Duration: 0.88 seconds
Result: PASS

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
module-param
Desc: Detect module_param changes
Duration: 0.28 seconds
Result: PASS

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
verify-fixes
Desc: Verifies that the Fixes: tags exist
Duration: 0.22 seconds
Result: PASS

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linux-riscv-bot commented Apr 2, 2026

Patch 1: "cmpxchg: allow const-qualified old value in cmpxchg()"
verify-signedoff
Desc: Verifies that Signed-off-by: tags are correct
Duration: 0.30 seconds
Result: PASS

@linux-riscv-bot linux-riscv-bot deleted the pw1076232 branch April 3, 2026 02:30
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