From 419123f900dac58fb27ce5285b21074f5300095a Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Thu, 19 Nov 2015 11:09:45 +0100 Subject: 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 Signed-off-by: Martin Schwidefsky --- arch/s390/lib/spinlock.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) (limited to 'arch/s390/lib') diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c index 0a68fe0..d4549c9 100644 --- a/arch/s390/lib/spinlock.c +++ b/arch/s390/lib/spinlock.c @@ -37,6 +37,15 @@ static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old) asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock)); } +static inline int cpu_is_preempted(int cpu) +{ + if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu)) + return 0; + if (smp_vcpu_scheduled(cpu)) + return 0; + return 1; +} + void arch_spin_lock_wait(arch_spinlock_t *lp) { unsigned int cpu = SPINLOCK_LOCKVAL; @@ -53,7 +62,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp) continue; } /* First iteration: check if the lock owner is running. */ - if (first_diag && !smp_vcpu_scheduled(~owner)) { + if (first_diag && cpu_is_preempted(~owner)) { smp_yield_cpu(~owner); first_diag = 0; continue; @@ -72,7 +81,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp) * yield the CPU unconditionally. For LPAR rely on the * sense running status. */ - if (!MACHINE_IS_LPAR || !smp_vcpu_scheduled(~owner)) { + if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) { smp_yield_cpu(~owner); first_diag = 0; } @@ -98,7 +107,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags) local_irq_restore(flags); } /* Check if the lock owner is running. */ - if (first_diag && !smp_vcpu_scheduled(~owner)) { + if (first_diag && cpu_is_preempted(~owner)) { smp_yield_cpu(~owner); first_diag = 0; continue; @@ -117,7 +126,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags) * yield the CPU unconditionally. For LPAR rely on the * sense running status. */ - if (!MACHINE_IS_LPAR || !smp_vcpu_scheduled(~owner)) { + if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) { smp_yield_cpu(~owner); first_diag = 0; } @@ -155,7 +164,7 @@ void _raw_read_lock_wait(arch_rwlock_t *rw) owner = 0; while (1) { if (count-- <= 0) { - if (owner && !smp_vcpu_scheduled(~owner)) + if (owner && cpu_is_preempted(~owner)) smp_yield_cpu(~owner); count = spin_retry; } @@ -201,7 +210,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev) owner = 0; while (1) { if (count-- <= 0) { - if (owner && !smp_vcpu_scheduled(~owner)) + if (owner && cpu_is_preempted(~owner)) smp_yield_cpu(~owner); count = spin_retry; } @@ -231,7 +240,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw) owner = 0; while (1) { if (count-- <= 0) { - if (owner && !smp_vcpu_scheduled(~owner)) + if (owner && cpu_is_preempted(~owner)) smp_yield_cpu(~owner); count = spin_retry; } @@ -275,7 +284,7 @@ void arch_lock_relax(unsigned int cpu) { if (!cpu) return; - if (MACHINE_IS_LPAR && smp_vcpu_scheduled(~cpu)) + if (MACHINE_IS_LPAR && !cpu_is_preempted(~cpu)) return; smp_yield_cpu(~cpu); } -- cgit v1.1