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authorHeiko Carstens <hca@linux.ibm.com>2022-05-06 12:33:19 +0300
committerHeiko Carstens <hca@linux.ibm.com>2022-05-11 15:40:58 +0300
commit63678eecec57fc51b778be3da35a397931287170 (patch)
treebcb49f8eb4c0824719baec46ce380bbc0e5c8cd6 /arch/s390
parent5ace65ebb5ce9fe1cc8fdbdd97079fb566ef0ea4 (diff)
downloadlinux-63678eecec57fc51b778be3da35a397931287170.tar.xz
s390/preempt: disable __preempt_count_add() optimization for PROFILE_ALL_BRANCHES
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>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/include/asm/preempt.h15
1 files changed, 11 insertions, 4 deletions
diff --git a/arch/s390/include/asm/preempt.h b/arch/s390/include/asm/preempt.h
index d9d5350cc3ec..bf15da0fedbc 100644
--- a/arch/s390/include/asm/preempt.h
+++ b/arch/s390/include/asm/preempt.h
@@ -46,10 +46,17 @@ 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)