From e98bbaafcd1c47d30f3245517fb585f1aaaca4db Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Mon, 22 Jun 2009 12:08:20 +0200 Subject: [S390] lockless idle time accounting Replace the spinlock used in the idle time accounting with a sequence counter mechanism analog to seqlock. Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/smp.c | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-) (limited to 'arch/s390/kernel/smp.c') diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index fd8e3111a4e8..2270730f5354 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -856,13 +856,20 @@ static ssize_t show_idle_count(struct sys_device *dev, { struct s390_idle_data *idle; unsigned long long idle_count; + unsigned int sequence; idle = &per_cpu(s390_idle, dev->id); - spin_lock(&idle->lock); +repeat: + sequence = idle->sequence; + smp_rmb(); + if (sequence & 1) + goto repeat; idle_count = idle->idle_count; if (idle->idle_enter) idle_count++; - spin_unlock(&idle->lock); + smp_rmb(); + if (idle->sequence != sequence) + goto repeat; return sprintf(buf, "%llu\n", idle_count); } static SYSDEV_ATTR(idle_count, 0444, show_idle_count, NULL); @@ -872,15 +879,22 @@ static ssize_t show_idle_time(struct sys_device *dev, { struct s390_idle_data *idle; unsigned long long now, idle_time, idle_enter; + unsigned int sequence; idle = &per_cpu(s390_idle, dev->id); - spin_lock(&idle->lock); now = get_clock(); +repeat: + sequence = idle->sequence; + smp_rmb(); + if (sequence & 1) + goto repeat; idle_time = idle->idle_time; idle_enter = idle->idle_enter; if (idle_enter != 0ULL && idle_enter < now) idle_time += now - idle_enter; - spin_unlock(&idle->lock); + smp_rmb(); + if (idle->sequence != sequence) + goto repeat; return sprintf(buf, "%llu\n", idle_time >> 12); } static SYSDEV_ATTR(idle_time_us, 0444, show_idle_time, NULL); @@ -908,11 +922,7 @@ static int __cpuinit smp_cpu_notify(struct notifier_block *self, case CPU_ONLINE: case CPU_ONLINE_FROZEN: idle = &per_cpu(s390_idle, cpu); - spin_lock_irq(&idle->lock); - idle->idle_enter = 0; - idle->idle_time = 0; - idle->idle_count = 0; - spin_unlock_irq(&idle->lock); + memset(idle, 0, sizeof(struct s390_idle_data)); if (sysfs_create_group(&s->kobj, &cpu_online_attr_group)) return NOTIFY_BAD; break; -- cgit v1.2.3 From 3a6ba4600d6fb913ddb0dd08843ad75405795883 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Fri, 24 Jul 2009 12:39:51 +0200 Subject: [S390] vdso: fix per cpu area allocation vdso per cpu area allocation in smp_prepare_cpus() happens with GFP_KERNEL but irqs disabled. Triggers this one: Badness at kernel/lockdep.c:2280 Modules linked in: CPU: 0 Not tainted 2.6.30 #2 Process swapper (pid: 1, task: 000000003fe88000, ksp: 000000003fe87eb8) Krnl PSW : 0400c00180000000 0000000000083360 (lockdep_trace_alloc+0xec/0xf8) [...] Call Trace: ([<00000000000832b6>] lockdep_trace_alloc+0x42/0xf8) [<00000000000b1880>] __alloc_pages_internal+0x3e8/0x5c4 [<00000000000b1b4a>] __get_free_pages+0x3a/0xb0 [<0000000000026546>] vdso_alloc_per_cpu+0x6a/0x18c [<00000000005eff82>] smp_prepare_cpus+0x322/0x594 [<00000000005e8232>] kernel_init+0x76/0x398 [<000000000001bb1e>] kernel_thread_starter+0x6/0xc [<000000000001bb18>] kernel_thread_starter+0x0/0xc Fix this by moving the allocation out of the irqs disabled section. Reported-by: Christian Borntraeger Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/smp.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'arch/s390/kernel/smp.c') diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index 2270730f5354..be2cae083406 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -687,13 +687,14 @@ void __init smp_prepare_cpus(unsigned int max_cpus) #ifndef CONFIG_64BIT if (MACHINE_HAS_IEEE) lowcore->extended_save_area_addr = (u32) save_area; -#else - if (vdso_alloc_per_cpu(smp_processor_id(), lowcore)) - BUG(); #endif set_prefix((u32)(unsigned long) lowcore); local_mcck_enable(); local_irq_enable(); +#ifdef CONFIG_64BIT + if (vdso_alloc_per_cpu(smp_processor_id(), &S390_lowcore)) + BUG(); +#endif for_each_possible_cpu(cpu) if (cpu != smp_processor_id()) smp_create_idle(cpu); -- cgit v1.2.3