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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2015-11-19 11:09:45 +0100 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2015-11-27 09:24:18 +0100 |
| commit | 419123f900dac58fb27ce5285b21074f5300095a (patch) | |
| tree | d0b0d72691d4e2e3df0e9f4d2e335bebc378fdeb /arch/s390/include/asm/processor.h | |
| parent | c6f70d3b8a32fdec60d3f78cb59423f056f16688 (diff) | |
| download | blackbird-obmc-linux-419123f900dac58fb27ce5285b21074f5300095a.tar.gz blackbird-obmc-linux-419123f900dac58fb27ce5285b21074f5300095a.zip | |
s390/spinlock: do not yield to a CPU in udelay/mdelay
It does not make sense to try to relinquish the time slice with diag 0x9c
to a CPU in a state that does not allow to schedule the CPU. The scenario
where this can happen is a CPU waiting in udelay/mdelay while holding a
spin-lock.
Add a CIF bit to tag a CPU in enabled wait and use it to detect that the
yield of a CPU will not be successful and skip the diagnose call.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/include/asm/processor.h')
| -rw-r--r-- | arch/s390/include/asm/processor.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h index b16c3d0a1b9f..5592c94ebe31 100644 --- a/arch/s390/include/asm/processor.h +++ b/arch/s390/include/asm/processor.h @@ -18,12 +18,14 @@ #define CIF_NOHZ_DELAY 2 /* delay HZ disable for a tick */ #define CIF_FPU 3 /* restore FPU registers */ #define CIF_IGNORE_IRQ 4 /* ignore interrupt (for udelay) */ +#define CIF_ENABLED_WAIT 5 /* in enabled wait state */ #define _CIF_MCCK_PENDING _BITUL(CIF_MCCK_PENDING) #define _CIF_ASCE _BITUL(CIF_ASCE) #define _CIF_NOHZ_DELAY _BITUL(CIF_NOHZ_DELAY) #define _CIF_FPU _BITUL(CIF_FPU) #define _CIF_IGNORE_IRQ _BITUL(CIF_IGNORE_IRQ) +#define _CIF_ENABLED_WAIT _BITUL(CIF_ENABLED_WAIT) #ifndef __ASSEMBLY__ @@ -52,6 +54,16 @@ static inline int test_cpu_flag(int flag) return !!(S390_lowcore.cpu_flags & (1UL << flag)); } +/* + * Test CIF flag of another CPU. The caller needs to ensure that + * CPU hotplug can not happen, e.g. by disabling preemption. + */ +static inline int test_cpu_flag_of(int flag, int cpu) +{ + struct _lowcore *lc = lowcore_ptr[cpu]; + return !!(lc->cpu_flags & (1UL << flag)); +} + #define arch_needs_cpu() test_cpu_flag(CIF_NOHZ_DELAY) /* |
