From: Heiko Carstens hca@linux.ibm.com
[ Upstream commit 63678eecec57fc51b778be3da35a397931287170 ]
gcc 12 does not (always) optimize away code that should only be generated if parameters are constant and within in a certain range. This depends on various obscure kernel config options, however in particular PROFILE_ALL_BRANCHES can trigger this compile error:
In function ‘__atomic_add_const’, inlined from ‘__preempt_count_add.part.0’ at ./arch/s390/include/asm/preempt.h:50:3: ./arch/s390/include/asm/atomic_ops.h:80:9: error: impossible constraint in ‘asm’ 80 | asm volatile( \ | ^~~
Workaround this by simply disabling the optimization for PROFILE_ALL_BRANCHES, since the kernel will be so slow, that this optimization won't matter at all.
Reported-by: Thomas Richter tmricht@linux.ibm.com Reviewed-by: Sven Schnelle svens@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/include/asm/preempt.h | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/arch/s390/include/asm/preempt.h b/arch/s390/include/asm/preempt.h index b5ea9e14c017..3dcd8ab3db73 100644 --- a/arch/s390/include/asm/preempt.h +++ b/arch/s390/include/asm/preempt.h @@ -52,10 +52,17 @@ static inline bool test_preempt_need_resched(void)
static inline void __preempt_count_add(int val) { - if (__builtin_constant_p(val) && (val >= -128) && (val <= 127)) - __atomic_add_const(val, &S390_lowcore.preempt_count); - else - __atomic_add(val, &S390_lowcore.preempt_count); + /* + * With some obscure config options and CONFIG_PROFILE_ALL_BRANCHES + * enabled, gcc 12 fails to handle __builtin_constant_p(). + */ + if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES)) { + if (__builtin_constant_p(val) && (val >= -128) && (val <= 127)) { + __atomic_add_const(val, &S390_lowcore.preempt_count); + return; + } + } + __atomic_add(val, &S390_lowcore.preempt_count); }
static inline void __preempt_count_sub(int val)