commit 71945968d8 upstream.
A recent change to the optimization pipeline in LLVM reveals some
fragility around the inlining of LoongArch's __percpu functions, which
manifests as a BUILD_BUG() failure:
In file included from kernel/sched/build_policy.c:17:
In file included from include/linux/sched/cputime.h:5:
In file included from include/linux/sched/signal.h:5:
In file included from include/linux/rculist.h:11:
In file included from include/linux/rcupdate.h:26:
In file included from include/linux/irqflags.h:18:
arch/loongarch/include/asm/percpu.h:97:3: error: call to '__compiletime_assert_51' declared with 'error' attribute: BUILD_BUG failed
97 | BUILD_BUG();
| ^
include/linux/build_bug.h:59:21: note: expanded from macro 'BUILD_BUG'
59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
| ^
include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
| ^
include/linux/compiler_types.h:425:2: note: expanded from macro 'compiletime_assert'
425 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^
include/linux/compiler_types.h:413:2: note: expanded from macro '_compiletime_assert'
413 | __compiletime_assert(condition, msg, prefix, suffix)
| ^
include/linux/compiler_types.h:406:4: note: expanded from macro '__compiletime_assert'
406 | prefix ## suffix(); \
| ^
<scratch space>:86:1: note: expanded from here
86 | __compiletime_assert_51
| ^
1 error generated.
If these functions are not inlined (which the compiler is free to do
even with functions marked with the standard 'inline' keyword), the
BUILD_BUG() in the default case cannot be eliminated since the compiler
cannot prove it is never used, resulting in a build failure due to the
error attribute.
Mark these functions as __always_inline to guarantee inlining so that
the BUILD_BUG() only triggers when the default case genuinely cannot be
eliminated due to an unexpected size.
Cc: <stable@vger.kernel.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/1955
Fixes: 46859ac8af ("LoongArch: Add multi-processor (SMP) support")
Link: 1a2e77cf9e
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
cff8bf67f1