From: Keith Owens Date: Thu, 5 Jan 2006 23:36:06 +0000 (+1100) Subject: [IA64] Add hotplug cpu to salinfo.c, replace semaphore with mutex X-Git-Tag: firefly_0821_release~38904^2~2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=e026cca0f2c09c4c28c902db6384fd8a412671d6;p=firefly-linux-kernel-4.4.55.git [IA64] Add hotplug cpu to salinfo.c, replace semaphore with mutex Add hotplug cpu support to salinfo.c. The cpu_event field is a cpumask so use the cpu_* macros consistently, replacing the existing mixture of cpu_* and *_bit macros. Instead of counting the number of outstanding events in a semaphore and trying to track that count over user space context, interrupt context, non-maskable interrupt context and cpu hotplug, replace the semaphore with a test for "any bits set" combined with a mutex. Modify the locking to make the test for "work to do" an atomic operation. Signed-off-by: Keith Owens Signed-off-by: Tony Luck --- diff --git a/arch/ia64/kernel/salinfo.c b/arch/ia64/kernel/salinfo.c index a87a162a3086..9d5a823479a3 100644 --- a/arch/ia64/kernel/salinfo.c +++ b/arch/ia64/kernel/salinfo.c @@ -3,7 +3,7 @@ * * Creates entries in /proc/sal for various system features. * - * Copyright (c) 2003 Silicon Graphics, Inc. All rights reserved. + * Copyright (c) 2003, 2006 Silicon Graphics, Inc. All rights reserved. * Copyright (c) 2003 Hewlett-Packard Co * Bjorn Helgaas * @@ -27,9 +27,17 @@ * mca.c may not pass a buffer, a NULL buffer just indicates that a new * record is available in SAL. * Replace some NR_CPUS by cpus_online, for hotplug cpu. + * + * Jan 5 2006 kaos@sgi.com + * Handle hotplug cpus coming online. + * Handle hotplug cpus going offline while they still have outstanding records. + * Use the cpu_* macros consistently. + * Replace the counting semaphore with a mutex and a test if the cpumask is non-empty. + * Modify the locking to make the test for "work to do" an atomic operation. */ #include +#include #include #include #include @@ -132,8 +140,8 @@ enum salinfo_state { }; struct salinfo_data { - volatile cpumask_t cpu_event; /* which cpus have outstanding events */ - struct semaphore sem; /* count of cpus with outstanding events (bits set in cpu_event) */ + cpumask_t cpu_event; /* which cpus have outstanding events */ + struct semaphore mutex; u8 *log_buffer; u64 log_size; u8 *oemdata; /* decoded oem data */ @@ -174,6 +182,21 @@ struct salinfo_platform_oemdata_parms { int ret; }; +/* Kick the mutex that tells user space that there is work to do. Instead of + * trying to track the state of the mutex across multiple cpus, in user + * context, interrupt context, non-maskable interrupt context and hotplug cpu, + * it is far easier just to grab the mutex if it is free then release it. + * + * This routine must be called with data_saved_lock held, to make the down/up + * operation atomic. + */ +static void +salinfo_work_to_do(struct salinfo_data *data) +{ + down_trylock(&data->mutex); + up(&data->mutex); +} + static void salinfo_platform_oemdata_cpu(void *context) { @@ -212,9 +235,9 @@ salinfo_log_wakeup(int type, u8 *buffer, u64 size, int irqsafe) BUG_ON(type >= ARRAY_SIZE(salinfo_log_name)); + if (irqsafe) + spin_lock_irqsave(&data_saved_lock, flags); if (buffer) { - if (irqsafe) - spin_lock_irqsave(&data_saved_lock, flags); for (i = 0, data_saved = data->data_saved; i < saved_size; ++i, ++data_saved) { if (!data_saved->buffer) break; @@ -232,13 +255,11 @@ salinfo_log_wakeup(int type, u8 *buffer, u64 size, int irqsafe) data_saved->size = size; data_saved->buffer = buffer; } - if (irqsafe) - spin_unlock_irqrestore(&data_saved_lock, flags); } - - if (!test_and_set_bit(smp_processor_id(), &data->cpu_event)) { - if (irqsafe) - up(&data->sem); + cpu_set(smp_processor_id(), data->cpu_event); + if (irqsafe) { + salinfo_work_to_do(data); + spin_unlock_irqrestore(&data_saved_lock, flags); } } @@ -249,20 +270,17 @@ static struct timer_list salinfo_timer; static void salinfo_timeout_check(struct salinfo_data *data) { - int i; + unsigned long flags; if (!data->open) return; - for_each_online_cpu(i) { - if (test_bit(i, &data->cpu_event)) { - /* double up() is not a problem, user space will see no - * records for the additional "events". - */ - up(&data->sem); - } + if (!cpus_empty(data->cpu_event)) { + spin_lock_irqsave(&data_saved_lock, flags); + salinfo_work_to_do(data); + spin_unlock_irqrestore(&data_saved_lock, flags); } } -static void +static void salinfo_timeout (unsigned long arg) { salinfo_timeout_check(salinfo_data + SAL_INFO_TYPE_MCA); @@ -290,16 +308,20 @@ salinfo_event_read(struct file *file, char __user *buffer, size_t count, loff_t int i, n, cpu = -1; retry: - if (down_trylock(&data->sem)) { + if (cpus_empty(data->cpu_event) && down_trylock(&data->mutex)) { if (file->f_flags & O_NONBLOCK) return -EAGAIN; - if (down_interruptible(&data->sem)) + if (down_interruptible(&data->mutex)) return -EINTR; } n = data->cpu_check; for (i = 0; i < NR_CPUS; i++) { - if (test_bit(n, &data->cpu_event) && cpu_online(n)) { + if (cpu_isset(n, data->cpu_event)) { + if (!cpu_online(n)) { + cpu_clear(n, data->cpu_event); + continue; + } cpu = n; break; } @@ -310,9 +332,6 @@ retry: if (cpu == -1) goto retry; - /* events are sticky until the user says "clear" */ - up(&data->sem); - /* for next read, start checking at next CPU */ data->cpu_check = cpu; if (++data->cpu_check == NR_CPUS) @@ -381,10 +400,8 @@ salinfo_log_release(struct inode *inode, struct file *file) static void call_on_cpu(int cpu, void (*fn)(void *), void *arg) { - cpumask_t save_cpus_allowed, new_cpus_allowed; - memcpy(&save_cpus_allowed, ¤t->cpus_allowed, sizeof(save_cpus_allowed)); - memset(&new_cpus_allowed, 0, sizeof(new_cpus_allowed)); - set_bit(cpu, &new_cpus_allowed); + cpumask_t save_cpus_allowed = current->cpus_allowed; + cpumask_t new_cpus_allowed = cpumask_of_cpu(cpu); set_cpus_allowed(current, new_cpus_allowed); (*fn)(arg); set_cpus_allowed(current, save_cpus_allowed); @@ -433,10 +450,10 @@ retry: if (!data->saved_num) call_on_cpu(cpu, salinfo_log_read_cpu, data); if (!data->log_size) { - data->state = STATE_NO_DATA; - clear_bit(cpu, &data->cpu_event); + data->state = STATE_NO_DATA; + cpu_clear(cpu, data->cpu_event); } else { - data->state = STATE_LOG_RECORD; + data->state = STATE_LOG_RECORD; } } @@ -473,27 +490,31 @@ static int salinfo_log_clear(struct salinfo_data *data, int cpu) { sal_log_record_header_t *rh; + unsigned long flags; + spin_lock_irqsave(&data_saved_lock, flags); data->state = STATE_NO_DATA; - if (!test_bit(cpu, &data->cpu_event)) + if (!cpu_isset(cpu, data->cpu_event)) { + spin_unlock_irqrestore(&data_saved_lock, flags); return 0; - down(&data->sem); - clear_bit(cpu, &data->cpu_event); + } + cpu_clear(cpu, data->cpu_event); if (data->saved_num) { - unsigned long flags; - spin_lock_irqsave(&data_saved_lock, flags); - shift1_data_saved(data, data->saved_num - 1 ); + shift1_data_saved(data, data->saved_num - 1); data->saved_num = 0; - spin_unlock_irqrestore(&data_saved_lock, flags); } + spin_unlock_irqrestore(&data_saved_lock, flags); rh = (sal_log_record_header_t *)(data->log_buffer); /* Corrected errors have already been cleared from SAL */ if (rh->severity != sal_log_severity_corrected) call_on_cpu(cpu, salinfo_log_clear_cpu, data); /* clearing a record may make a new record visible */ salinfo_log_new_read(cpu, data); - if (data->state == STATE_LOG_RECORD && - !test_and_set_bit(cpu, &data->cpu_event)) - up(&data->sem); + if (data->state == STATE_LOG_RECORD) { + spin_lock_irqsave(&data_saved_lock, flags); + cpu_set(cpu, data->cpu_event); + salinfo_work_to_do(data); + spin_unlock_irqrestore(&data_saved_lock, flags); + } return 0; } @@ -550,6 +571,53 @@ static struct file_operations salinfo_data_fops = { .write = salinfo_log_write, }; +#ifdef CONFIG_HOTPLUG_CPU +static int __devinit +salinfo_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu) +{ + unsigned int i, cpu = (unsigned long)hcpu; + unsigned long flags; + struct salinfo_data *data; + switch (action) { + case CPU_ONLINE: + spin_lock_irqsave(&data_saved_lock, flags); + for (i = 0, data = salinfo_data; + i < ARRAY_SIZE(salinfo_data); + ++i, ++data) { + cpu_set(cpu, data->cpu_event); + salinfo_work_to_do(data); + } + spin_unlock_irqrestore(&data_saved_lock, flags); + break; + case CPU_DEAD: + spin_lock_irqsave(&data_saved_lock, flags); + for (i = 0, data = salinfo_data; + i < ARRAY_SIZE(salinfo_data); + ++i, ++data) { + struct salinfo_data_saved *data_saved; + int j; + for (j = ARRAY_SIZE(data->data_saved) - 1, data_saved = data->data_saved + j; + j >= 0; + --j, --data_saved) { + if (data_saved->buffer && data_saved->cpu == cpu) { + shift1_data_saved(data, j); + } + } + cpu_clear(cpu, data->cpu_event); + } + spin_unlock_irqrestore(&data_saved_lock, flags); + break; + } + return NOTIFY_OK; +} + +static struct notifier_block salinfo_cpu_notifier = +{ + .notifier_call = salinfo_cpu_callback, + .priority = 0, +}; +#endif /* CONFIG_HOTPLUG_CPU */ + static int __init salinfo_init(void) { @@ -557,7 +625,7 @@ salinfo_init(void) struct proc_dir_entry **sdir = salinfo_proc_entries; /* keeps track of every entry */ struct proc_dir_entry *dir, *entry; struct salinfo_data *data; - int i, j, online; + int i, j; salinfo_dir = proc_mkdir("sal", NULL); if (!salinfo_dir) @@ -572,7 +640,7 @@ salinfo_init(void) for (i = 0; i < ARRAY_SIZE(salinfo_log_name); i++) { data = salinfo_data + i; data->type = i; - sema_init(&data->sem, 0); + init_MUTEX(&data->mutex); dir = proc_mkdir(salinfo_log_name[i], salinfo_dir); if (!dir) continue; @@ -592,12 +660,8 @@ salinfo_init(void) *sdir++ = entry; /* we missed any events before now */ - online = 0; - for_each_online_cpu(j) { - set_bit(j, &data->cpu_event); - ++online; - } - sema_init(&data->sem, online); + for_each_online_cpu(j) + cpu_set(j, data->cpu_event); *sdir++ = dir; } @@ -609,6 +673,10 @@ salinfo_init(void) salinfo_timer.function = &salinfo_timeout; add_timer(&salinfo_timer); +#ifdef CONFIG_HOTPLUG_CPU + register_cpu_notifier(&salinfo_cpu_notifier); +#endif + return 0; }