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seqlock: Allow UBSAN_ALIGNMENT to fail optimizing

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With gcc-15 and gcc-16 with UBSAN_ALIGNMENT enabled the compiler fails to
inline and optimize __scoped_seqlock_bug() away on s390:

s390x-16.1.0-ld: kernel/sched/build_policy.o: in function `__scoped_seqlock_next':
/.../seqlock.h:1286:(.text+0x22030): undefined reference to `__scoped_seqlock_bug'

Fix this by adding UBSAN_ALIGNMENT to the list of config options where a
not inlined empty __scoped_seqlock_bug() is allowed.

Closes: https://lore.kernel.org/r/20260515092057.810542-1-arnd@kernel.org/
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260519110315.1385307-1-hca@linux.ibm.com
This commit is contained in:
Heiko Carstens 2026-05-19 13:03:15 +02:00 committed by Peter Zijlstra
parent a9e4e50519
commit 88331c4ec2
1 changed files with 4 additions and 3 deletions
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7
include/linux/seqlock.h
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@ -1259,14 +1259,15 @@ static __always_inline void __scoped_seqlock_cleanup(struct ss_tmp *sst)
extern void __scoped_seqlock_invalid_target(void);
#if (defined(CONFIG_CC_IS_GCC) && CONFIG_GCC_VERSION < 90000) || defined(CONFIG_KASAN)
#if (defined(CONFIG_CC_IS_GCC) && CONFIG_GCC_VERSION < 90000) || \
defined(CONFIG_KASAN) || defined(CONFIG_UBSAN_ALIGNMENT)
/*
* For some reason some GCC-8 architectures (nios2, alpha) have trouble
* determining that the ss_done state is impossible in __scoped_seqlock_next()
* below.
*
* Similarly KASAN is known to confuse compilers enough to break this. But we
* don't care about code quality for KASAN builds anyway.
* Similarly KASAN and UBSAN_ALIGNMENT are known to confuse compilers enough
* to break this. But we don't care about code quality for such builds anyway.
*/
static inline void __scoped_seqlock_bug(void) { }
#else