Commit 0d24f1b7 authored Dec 13, 2022 by Nathan Chancellor Committed by Masahiro Yamada Dec 14, 2022

padata: Mark padata_work_init() as __ref

When building arm64 allmodconfig + ThinLTO with clang and a proposed
modpost update to account for -ffuncton-sections, the following warning
appears:

WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text)
WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text)

LLVM has optimized padata_work_init() to include the address of
padata_mt_helper() directly because it inlined the other call to
padata_work_init() with padata_parallel_worker(), meaning the remaining
uses of padata_work_init() use padata_mt_helper() as the work_fn
argument. This optimization causes modpost to complain since
padata_work_init() is not __init, whereas padata_mt_helper() is.

Since padata_work_init() is only called from __init code when
padata_mt_helper() is passed as the work_fn argument, mark
padata_work_init() as __ref, which makes it clear to modpost that this
scenario is okay.

Suggested-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

parent 87d599fc

kernel/padata.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -83,7 +83,15 @@ static struct padata_work *padata_work_alloc(void)
		return pw;
		}

		static void padata_work_init(struct padata_work *pw, work_func_t work_fn,
		/*
		* This function is marked __ref because this function may be optimized in such
		* a way that it directly refers to work_fn's address, which causes modpost to
		* complain when work_fn is marked __init. This scenario was observed with clang
		* LTO, where padata_work_init() was optimized to refer directly to
		* padata_mt_helper() because the calls to padata_work_init() with other work_fn
		* values were eliminated or inlined.
		*/
		static void __ref padata_work_init(struct padata_work *pw, work_func_t work_fn,
		void *data, int flags)
		{
		if (flags & PADATA_WORK_ONSTACK)