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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>
This commit is contained in:
Nathan Chancellor 2022-12-13 11:35:28 -07:00 committed by Masahiro Yamada
parent 87d599fc39
commit 0d24f1b7cc
1 changed files with 10 additions and 2 deletions
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12
kernel/padata.c
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@ -83,8 +83,16 @@ static struct padata_work *padata_work_alloc(void)
return pw;
}
static void padata_work_init(struct padata_work *pw, work_func_t work_fn,
void *data, int flags)
/*
* 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)
INIT_WORK_ONSTACK(&pw->pw_work, work_fn);