diff options
Diffstat (limited to 'kernel/trace/ring_buffer.c')
| -rw-r--r-- | kernel/trace/ring_buffer.c | 2014 |
1 files changed, 2014 insertions, 0 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c new file mode 100644 index 000000000000..94af1fe56bb4 --- /dev/null +++ b/kernel/trace/ring_buffer.c @@ -0,0 +1,2014 @@ +/* + * Generic ring buffer + * + * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> + */ +#include <linux/ring_buffer.h> +#include <linux/spinlock.h> +#include <linux/debugfs.h> +#include <linux/uaccess.h> +#include <linux/module.h> +#include <linux/percpu.h> +#include <linux/mutex.h> +#include <linux/sched.h> /* used for sched_clock() (for now) */ +#include <linux/init.h> +#include <linux/hash.h> +#include <linux/list.h> +#include <linux/fs.h> + +/* Up this if you want to test the TIME_EXTENTS and normalization */ +#define DEBUG_SHIFT 0 + +/* FIXME!!! */ +u64 ring_buffer_time_stamp(int cpu) +{ + /* shift to debug/test normalization and TIME_EXTENTS */ + return sched_clock() << DEBUG_SHIFT; +} + +void ring_buffer_normalize_time_stamp(int cpu, u64 *ts) +{ + /* Just stupid testing the normalize function and deltas */ + *ts >>= DEBUG_SHIFT; +} + +#define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event)) +#define RB_ALIGNMENT_SHIFT 2 +#define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT) +#define RB_MAX_SMALL_DATA 28 + +enum { + RB_LEN_TIME_EXTEND = 8, + RB_LEN_TIME_STAMP = 16, +}; + +/* inline for ring buffer fast paths */ +static inline unsigned +rb_event_length(struct ring_buffer_event *event) +{ + unsigned length; + + switch (event->type) { + case RINGBUF_TYPE_PADDING: + /* undefined */ + return -1; + + case RINGBUF_TYPE_TIME_EXTEND: + return RB_LEN_TIME_EXTEND; + + case RINGBUF_TYPE_TIME_STAMP: + return RB_LEN_TIME_STAMP; + + case RINGBUF_TYPE_DATA: + if (event->len) + length = event->len << RB_ALIGNMENT_SHIFT; + else + length = event->array[0]; + return length + RB_EVNT_HDR_SIZE; + default: + BUG(); + } + /* not hit */ + return 0; +} + +/** + * ring_buffer_event_length - return the length of the event + * @event: the event to get the length of + */ +unsigned ring_buffer_event_length(struct ring_buffer_event *event) +{ + return rb_event_length(event); +} + +/* inline for ring buffer fast paths */ +static inline void * +rb_event_data(struct ring_buffer_event *event) +{ + BUG_ON(event->type != RINGBUF_TYPE_DATA); + /* If length is in len field, then array[0] has the data */ + if (event->len) + return (void *)&event->array[0]; + /* Otherwise length is in array[0] and array[1] has the data */ + return (void *)&event->array[1]; +} + +/** + * ring_buffer_event_data - return the data of the event + * @event: the event to get the data from + */ +void *ring_buffer_event_data(struct ring_buffer_event *event) +{ + return rb_event_data(event); +} + +#define for_each_buffer_cpu(buffer, cpu) \ + for_each_cpu_mask(cpu, buffer->cpumask) + +#define TS_SHIFT 27 +#define TS_MASK ((1ULL << TS_SHIFT) - 1) +#define TS_DELTA_TEST (~TS_MASK) + +/* + * This hack stolen from mm/slob.c. + * We can store per page timing information in the page frame of the page. + * Thanks to Peter Zijlstra for suggesting this idea. + */ +struct buffer_page { + u64 time_stamp; /* page time stamp */ + local_t write; /* index for next write */ + local_t commit; /* write commited index */ + unsigned read; /* index for next read */ + struct list_head list; /* list of free pages */ + void *page; /* Actual data page */ +}; + +/* + * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing + * this issue out. + */ +static inline void free_buffer_page(struct buffer_page *bpage) +{ + if (bpage->page) + __free_page(bpage->page); + kfree(bpage); +} + +/* + * We need to fit the time_stamp delta into 27 bits. + */ +static inline int test_time_stamp(u64 delta) +{ + if (delta & TS_DELTA_TEST) + return 1; + return 0; +} + +#define BUF_PAGE_SIZE PAGE_SIZE + +/* + * head_page == tail_page && head == tail then buffer is empty. + */ +struct ring_buffer_per_cpu { + int cpu; + struct ring_buffer *buffer; + spinlock_t lock; + struct lock_class_key lock_key; + struct list_head pages; + struct buffer_page *head_page; /* read from head */ + struct buffer_page *tail_page; /* write to tail */ + struct buffer_page *commit_page; /* commited pages */ + struct buffer_page *reader_page; + unsigned long overrun; + unsigned long entries; + u64 write_stamp; + u64 read_stamp; + atomic_t record_disabled; +}; + +struct ring_buffer { + unsigned long size; + unsigned pages; + unsigned flags; + int cpus; + cpumask_t cpumask; + atomic_t record_disabled; + + struct mutex mutex; + + struct ring_buffer_per_cpu **buffers; +}; + +struct ring_buffer_iter { + struct ring_buffer_per_cpu *cpu_buffer; + unsigned long head; + struct buffer_page *head_page; + u64 read_stamp; +}; + +#define RB_WARN_ON(buffer, cond) \ + do { \ + if (unlikely(cond)) { \ + atomic_inc(&buffer->record_disabled); \ + WARN_ON(1); \ + } \ + } while (0) + +#define RB_WARN_ON_RET(buffer, cond) \ + do { \ + if (unlikely(cond)) { \ + atomic_inc(&buffer->record_disabled); \ + WARN_ON(1); \ + return -1; \ + } \ + } while (0) + +#define RB_WARN_ON_ONCE(buffer, cond) \ + do { \ + static int once; \ + if (unlikely(cond) && !once) { \ + once++; \ + atomic_inc(&buffer->record_disabled); \ + WARN_ON(1); \ + } \ + } while (0) + +/** + * check_pages - integrity check of buffer pages + * @cpu_buffer: CPU buffer with pages to test + * + * As a safty measure we check to make sure the data pages have not + * been corrupted. + */ +static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) +{ + struct list_head *head = &cpu_buffer->pages; + struct buffer_page *page, *tmp; + + RB_WARN_ON_RET(cpu_buffer, head->next->prev != head); + RB_WARN_ON_RET(cpu_buffer, head->prev->next != head); + + list_for_each_entry_safe(page, tmp, head, list) { + RB_WARN_ON_RET(cpu_buffer, + page->list.next->prev != &page->list); + RB_WARN_ON_RET(cpu_buffer, + page->list.prev->next != &page->list); + } + + return 0; +} + +static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, + unsigned nr_pages) +{ + struct list_head *head = &cpu_buffer->pages; + struct buffer_page *page, *tmp; + unsigned long addr; + LIST_HEAD(pages); + unsigned i; + + for (i = 0; i < nr_pages; i++) { + page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()), + GFP_KERNEL, cpu_to_node(cpu_buffer->cpu)); + if (!page) + goto free_pages; + list_add(&page->list, &pages); + + addr = __get_free_page(GFP_KERNEL); + if (!addr) + goto free_pages; + page->page = (void *)addr; + } + + list_splice(&pages, head); + + rb_check_pages(cpu_buffer); + + return 0; + + free_pages: + list_for_each_entry_safe(page, tmp, &pages, list) { + list_del_init(&page->list); + free_buffer_page(page); + } + return -ENOMEM; +} + +static struct ring_buffer_per_cpu * +rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + struct buffer_page *page; + unsigned long addr; + int ret; + + cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), + GFP_KERNEL, cpu_to_node(cpu)); + if (!cpu_buffer) + return NULL; + + cpu_buffer->cpu = cpu; + cpu_buffer->buffer = buffer; + spin_lock_init(&cpu_buffer->lock); + INIT_LIST_HEAD(&cpu_buffer->pages); + + page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()), + GFP_KERNEL, cpu_to_node(cpu)); + if (!page) + goto fail_free_buffer; + + cpu_buffer->reader_page = page; + addr = __get_free_page(GFP_KERNEL); + if (!addr) + goto fail_free_reader; + page->page = (void *)addr; + + INIT_LIST_HEAD(&cpu_buffer->reader_page->list); + + ret = rb_allocate_pages(cpu_buffer, buffer->pages); + if (ret < 0) + goto fail_free_reader; + + cpu_buffer->head_page + = list_entry(cpu_buffer->pages.next, struct buffer_page, list); + cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; + + return cpu_buffer; + + fail_free_reader: + free_buffer_page(cpu_buffer->reader_page); + + fail_free_buffer: + kfree(cpu_buffer); + return NULL; +} + +static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) +{ + struct list_head *head = &cpu_buffer->pages; + struct buffer_page *page, *tmp; + + list_del_init(&cpu_buffer->reader_page->list); + free_buffer_page(cpu_buffer->reader_page); + + list_for_each_entry_safe(page, tmp, head, list) { + list_del_init(&page->list); + free_buffer_page(page); + } + kfree(cpu_buffer); +} + +/* + * Causes compile errors if the struct buffer_page gets bigger + * than the struct page. + */ +extern int ring_buffer_page_too_big(void); + +/** + * ring_buffer_alloc - allocate a new ring_buffer + * @size: the size in bytes that is needed. + * @flags: attributes to set for the ring buffer. + * + * Currently the only flag that is available is the RB_FL_OVERWRITE + * flag. This flag means that the buffer will overwrite old data + * when the buffer wraps. If this flag is not set, the buffer will + * drop data when the tail hits the head. + */ +struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags) +{ + struct ring_buffer *buffer; + int bsize; + int cpu; + + /* Paranoid! Optimizes out when all is well */ + if (sizeof(struct buffer_page) > sizeof(struct page)) + ring_buffer_page_too_big(); + + + /* keep it in its own cache line */ + buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), + GFP_KERNEL); + if (!buffer) + return NULL; + + buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); + buffer->flags = flags; + + /* need at least two pages */ + if (buffer->pages == 1) + buffer->pages++; + + buffer->cpumask = cpu_possible_map; + buffer->cpus = nr_cpu_ids; + + bsize = sizeof(void *) * nr_cpu_ids; + buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), + GFP_KERNEL); + if (!buffer->buffers) + goto fail_free_buffer; + + for_each_buffer_cpu(buffer, cpu) { + buffer->buffers[cpu] = + rb_allocate_cpu_buffer(buffer, cpu); + if (!buffer->buffers[cpu]) + goto fail_free_buffers; + } + + mutex_init(&buffer->mutex); + + return buffer; + + fail_free_buffers: + for_each_buffer_cpu(buffer, cpu) { + if (buffer->buffers[cpu]) + rb_free_cpu_buffer(buffer->buffers[cpu]); + } + kfree(buffer->buffers); + + fail_free_buffer: + kfree(buffer); + return NULL; +} + +/** + * ring_buffer_free - free a ring buffer. + * @buffer: the buffer to free. + */ +void +ring_buffer_free(struct ring_buffer *buffer) +{ + int cpu; + + for_each_buffer_cpu(buffer, cpu) + rb_free_cpu_buffer(buffer->buffers[cpu]); + + kfree(buffer); +} + +static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); + +static void +rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) +{ + struct buffer_page *page; + struct list_head *p; + unsigned i; + + atomic_inc(&cpu_buffer->record_disabled); + synchronize_sched(); + + for (i = 0; i < nr_pages; i++) { + BUG_ON(list_empty(&cpu_buffer->pages)); + p = cpu_buffer->pages.next; + page = list_entry(p, struct buffer_page, list); + list_del_init(&page->list); + free_buffer_page(page); + } + BUG_ON(list_empty(&cpu_buffer->pages)); + + rb_reset_cpu(cpu_buffer); + + rb_check_pages(cpu_buffer); + + atomic_dec(&cpu_buffer->record_disabled); + +} + +static void +rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, + struct list_head *pages, unsigned nr_pages) +{ + struct buffer_page *page; + struct list_head *p; + unsigned i; + + atomic_inc(&cpu_buffer->record_disabled); + synchronize_sched(); + + for (i = 0; i < nr_pages; i++) { + BUG_ON(list_empty(pages)); + p = pages->next; + page = list_entry(p, struct buffer_page, list); + list_del_init(&page->list); + list_add_tail(&page->list, &cpu_buffer->pages); + } + rb_reset_cpu(cpu_buffer); + + rb_check_pages(cpu_buffer); + + atomic_dec(&cpu_buffer->record_disabled); +} + +/** + * ring_buffer_resize - resize the ring buffer + * @buffer: the buffer to resize. + * @size: the new size. + * + * The tracer is responsible for making sure that the buffer is + * not being used while changing the size. + * Note: We may be able to change the above requirement by using + * RCU synchronizations. + * + * Minimum size is 2 * BUF_PAGE_SIZE. + * + * Returns -1 on failure. + */ +int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) +{ + struct ring_buffer_per_cpu *cpu_buffer; + unsigned nr_pages, rm_pages, new_pages; + struct buffer_page *page, *tmp; + unsigned long buffer_size; + unsigned long addr; + LIST_HEAD(pages); + int i, cpu; + + size = DIV_ROUND_UP(size, BUF_PAGE_SIZE); + size *= BUF_PAGE_SIZE; + buffer_size = buffer->pages * BUF_PAGE_SIZE; + + /* we need a minimum of two pages */ + if (size < BUF_PAGE_SIZE * 2) + size = BUF_PAGE_SIZE * 2; + + if (size == buffer_size) + return size; + + mutex_lock(&buffer->mutex); + + nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); + + if (size < buffer_size) { + + /* easy case, just free pages */ + BUG_ON(nr_pages >= buffer->pages); + + rm_pages = buffer->pages - nr_pages; + + for_each_buffer_cpu(buffer, cpu) { + cpu_buffer = buffer->buffers[cpu]; + rb_remove_pages(cpu_buffer, rm_pages); + } + goto out; + } + + /* + * This is a bit more difficult. We only want to add pages + * when we can allocate enough for all CPUs. We do this + * by allocating all the pages and storing them on a local + * link list. If we succeed in our allocation, then we + * add these pages to the cpu_buffers. Otherwise we just free + * them all and return -ENOMEM; + */ + BUG_ON(nr_pages <= buffer->pages); + new_pages = nr_pages - buffer->pages; + + for_each_buffer_cpu(buffer, cpu) { + for (i = 0; i < new_pages; i++) { + page = kzalloc_node(ALIGN(sizeof(*page), + cache_line_size()), + GFP_KERNEL, cpu_to_node(cpu)); + if (!page) + goto free_pages; + list_add(&page->list, &pages); + addr = __get_free_page(GFP_KERNEL); + if (!addr) + goto free_pages; + page->page = (void *)addr; + } + } + + for_each_buffer_cpu(buffer, cpu) { + cpu_buffer = buffer->buffers[cpu]; + rb_insert_pages(cpu_buffer, &pages, new_pages); + } + + BUG_ON(!list_empty(&pages)); + + out: + buffer->pages = nr_pages; + mutex_unlock(&buffer->mutex); + + return size; + + free_pages: + list_for_each_entry_safe(page, tmp, &pages, list) { + list_del_init(&page->list); + free_buffer_page(page); + } + return -ENOMEM; +} + +static inline int rb_null_event(struct ring_buffer_event *event) +{ + return event->type == RINGBUF_TYPE_PADDING; +} + +static inline void *__rb_page_index(struct buffer_page *page, unsigned index) +{ + return page->page + index; +} + +static inline struct ring_buffer_event * +rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) +{ + return __rb_page_index(cpu_buffer->reader_page, + cpu_buffer->reader_page->read); +} + +static inline struct ring_buffer_event * +rb_head_event(struct ring_buffer_per_cpu *cpu_buffer) +{ + return __rb_page_index(cpu_buffer->head_page, + cpu_buffer->head_page->read); +} + +static inline struct ring_buffer_event * +rb_iter_head_event(struct ring_buffer_iter *iter) +{ + return __rb_page_index(iter->head_page, iter->head); +} + +static inline unsigned rb_page_write(struct buffer_page *bpage) +{ + return local_read(&bpage->write); +} + +static inline unsigned rb_page_commit(struct buffer_page *bpage) +{ + return local_read(&bpage->commit); +} + +/* Size is determined by what has been commited */ +static inline unsigned rb_page_size(struct buffer_page *bpage) +{ + return rb_page_commit(bpage); +} + +static inline unsigned +rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) +{ + return rb_page_commit(cpu_buffer->commit_page); +} + +static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer) +{ + return rb_page_commit(cpu_buffer->head_page); +} + +/* + * When the tail hits the head and the buffer is in overwrite mode, + * the head jumps to the next page and all content on the previous + * page is discarded. But before doing so, we update the overrun + * variable of the buffer. + */ +static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer) +{ + struct ring_buffer_event *event; + unsigned long head; + + for (head = 0; head < rb_head_size(cpu_buffer); + head += rb_event_length(event)) { + + event = __rb_page_index(cpu_buffer->head_page, head); + BUG_ON(rb_null_event(event)); + /* Only count data entries */ + if (event->type != RINGBUF_TYPE_DATA) + continue; + cpu_buffer->overrun++; + cpu_buffer->entries--; + } +} + +static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, + struct buffer_page **page) +{ + struct list_head *p = (*page)->list.next; + + if (p == &cpu_buffer->pages) + p = p->next; + + *page = list_entry(p, struct buffer_page, list); +} + +static inline unsigned +rb_event_index(struct ring_buffer_event *event) +{ + unsigned long addr = (unsigned long)event; + + return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE); +} + +static inline int +rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer, + struct ring_buffer_event *event) +{ + unsigned long addr = (unsigned long)event; + unsigned long index; + + index = rb_event_index(event); + addr &= PAGE_MASK; + + return cpu_buffer->commit_page->page == (void *)addr && + rb_commit_index(cpu_buffer) == index; +} + +static inline void +rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer, + struct ring_buffer_event *event) +{ + unsigned long addr = (unsigned long)event; + unsigned long index; + + index = rb_event_index(event); + addr &= PAGE_MASK; + + while (cpu_buffer->commit_page->page != (void *)addr) { + RB_WARN_ON(cpu_buffer, + cpu_buffer->commit_page == cpu_buffer->tail_page); + cpu_buffer->commit_page->commit = + cpu_buffer->commit_page->write; + rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); + cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp; + } + + /* Now set the commit to the event's index */ + local_set(&cpu_buffer->commit_page->commit, index); +} + +static inline void +rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) +{ + /* + * We only race with interrupts and NMIs on this CPU. + * If we own the commit event, then we can commit + * all others that interrupted us, since the interruptions + * are in stack format (they finish before they come + * back to us). This allows us to do a simple loop to + * assign the commit to the tail. + */ + while (cpu_buffer->commit_page != cpu_buffer->tail_page) { + cpu_buffer->commit_page->commit = + cpu_buffer->commit_page->write; + rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); + cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp; + /* add barrier to keep gcc from optimizing too much */ + barrier(); + } + while (rb_commit_index(cpu_buffer) != + rb_page_write(cpu_buffer->commit_page)) { + cpu_buffer->commit_page->commit = + cpu_buffer->commit_page->write; + barrier(); + } +} + +static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer) +{ + cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp; + cpu_buffer->reader_page->read = 0; +} + +static inline void rb_inc_iter(struct ring_buffer_iter *iter) +{ + struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; + + /* + * The iterator could be on the reader page (it starts there). + * But the head could have moved, since the reader was + * found. Check for this case and assign the iterator + * to the head page instead of next. + */ + if (iter->head_page == cpu_buffer->reader_page) + iter->head_page = cpu_buffer->head_page; + else + rb_inc_page(cpu_buffer, &iter->head_page); + + iter->read_stamp = iter->head_page->time_stamp; + iter->head = 0; +} + +/** + * ring_buffer_update_event - update event type and data + * @event: the even to update + * @type: the type of event + * @length: the size of the event field in the ring buffer + * + * Update the type and data fields of the event. The length + * is the actual size that is written to the ring buffer, + * and with this, we can determine what to place into the + * data field. + */ +static inline void +rb_update_event(struct ring_buffer_event *event, + unsigned type, unsigned length) +{ + event->type = type; + + switch (type) { + + case RINGBUF_TYPE_PADDING: + break; + + case RINGBUF_TYPE_TIME_EXTEND: + event->len = + (RB_LEN_TIME_EXTEND + (RB_ALIGNMENT-1)) + >> RB_ALIGNMENT_SHIFT; + break; + + case RINGBUF_TYPE_TIME_STAMP: + event->len = + (RB_LEN_TIME_STAMP + (RB_ALIGNMENT-1)) + >> RB_ALIGNMENT_SHIFT; + break; + + case RINGBUF_TYPE_DATA: + length -= RB_EVNT_HDR_SIZE; + if (length > RB_MAX_SMALL_DATA) { + event->len = 0; + event->array[0] = length; + } else + event->len = + (length + (RB_ALIGNMENT-1)) + >> RB_ALIGNMENT_SHIFT; + break; + default: + BUG(); + } +} + +static inline unsigned rb_calculate_event_length(unsigned length) +{ + struct ring_buffer_event event; /* Used only for sizeof array */ + + /* zero length can cause confusions */ + if (!length) + length = 1; + + if (length > RB_MAX_SMALL_DATA) + length += sizeof(event.array[0]); + + length += RB_EVNT_HDR_SIZE; + length = ALIGN(length, RB_ALIGNMENT); + + return length; +} + +static struct ring_buffer_event * +__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, + unsigned type, unsigned long length, u64 *ts) +{ + struct buffer_page *tail_page, *head_page, *reader_page; + unsigned long tail, write; + struct ring_buffer *buffer = cpu_buffer->buffer; + struct ring_buffer_event *event; + unsigned long flags; + + tail_page = cpu_buffer->tail_page; + write = local_add_return(length, &tail_page->write); + tail = write - length; + + /* See if we shot pass the end of this buffer page */ + if (write > BUF_PAGE_SIZE) { + struct buffer_page *next_page = tail_page; + + spin_lock_irqsave(&cpu_buffer->lock, flags); + + rb_inc_page(cpu_buffer, &next_page); + + head_page = cpu_buffer->head_page; + reader_page = cpu_buffer->reader_page; + + /* we grabbed the lock before incrementing */ + RB_WARN_ON(cpu_buffer, next_page == reader_page); + + /* + * If for some reason, we had an interrupt storm that made + * it all the way around the buffer, bail, and warn + * about it. + */ + if (unlikely(next_page == cpu_buffer->commit_page)) { + WARN_ON_ONCE(1); + goto out_unlock; + } + + if (next_page == head_page) { + if (!(buffer->flags & RB_FL_OVERWRITE)) { + /* reset write */ + if (tail <= BUF_PAGE_SIZE) + local_set(&tail_page->write, tail); + goto out_unlock; + } + + /* tail_page has not moved yet? */ + if (tail_page == cpu_buffer->tail_page) { + /* count overflows */ + rb_update_overflow(cpu_buffer); + + rb_inc_page(cpu_buffer, &head_page); + cpu_buffer->head_page = head_page; + cpu_buffer->head_page->read = 0; + } + } + + /* + * If the tail page is still the same as what we think + * it is, then it is up to us to update the tail + * pointer. + */ + if (tail_page == cpu_buffer->tail_page) { + local_set(&next_page->write, 0); + local_set(&next_page->commit, 0); + cpu_buffer->tail_page = next_page; + + /* reread the time stamp */ + *ts = ring_buffer_time_stamp(cpu_buffer->cpu); + cpu_buffer->tail_page->time_stamp = *ts; + } + + /* + * The actual tail page has moved forward. + */ + if (tail < BUF_PAGE_SIZE) { + /* Mark the rest of the page with padding */ + event = __rb_page_index(tail_page, tail); + event->type = RINGBUF_TYPE_PADDING; + } + + if (tail <= BUF_PAGE_SIZE) + /* Set the write back to the previous setting */ + local_set(&tail_page->write, tail); + + /* + * If this was a commit entry that failed, + * increment that too + */ + if (tail_page == cpu_buffer->commit_page && + tail == rb_commit_index(cpu_buffer)) { + rb_set_commit_to_write(cpu_buffer); + } + + spin_unlock_irqrestore(&cpu_buffer->lock, flags); + + /* fail and let the caller try again */ + return ERR_PTR(-EAGAIN); + } + + /* We reserved something on the buffer */ + + BUG_ON(write > BUF_PAGE_SIZE); + + event = __rb_page_index(tail_page, tail); + rb_update_event(event, type, length); + + /* + * If this is a commit and the tail is zero, then update + * this page's time stamp. + */ + if (!tail && rb_is_commit(cpu_buffer, event)) + cpu_buffer->commit_page->time_stamp = *ts; + + return event; + + out_unlock: + spin_unlock_irqrestore(&cpu_buffer->lock, flags); + return NULL; +} + +static int +rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer, + u64 *ts, u64 *delta) +{ + struct ring_buffer_event *event; + static int once; + int ret; + + if (unlikely(*delta > (1ULL << 59) && !once++)) { + printk(KERN_WARNING "Delta way too big! %llu" + " ts=%llu write stamp = %llu\n", + *delta, *ts, cpu_buffer->write_stamp); + WARN_ON(1); + } + + /* + * The delta is too big, we to add a + * new timestamp. + */ + event = __rb_reserve_next(cpu_buffer, + RINGBUF_TYPE_TIME_EXTEND, + RB_LEN_TIME_EXTEND, + ts); + if (!event) + return -EBUSY; + + if (PTR_ERR(event) == -EAGAIN) + return -EAGAIN; + + /* Only a commited time event can update the write stamp */ + if (rb_is_commit(cpu_buffer, event)) { + /* + * If this is the first on the page, then we need to + * update the page itself, and just put in a zero. + */ + if (rb_event_index(event)) { + event->time_delta = *delta & TS_MASK; + event->array[0] = *delta >> TS_SHIFT; + } else { + cpu_buffer->commit_page->time_stamp = *ts; + event->time_delta = 0; + event->array[0] = 0; + } + cpu_buffer->write_stamp = *ts; + /* let the caller know this was the commit */ + ret = 1; + } else { + /* Darn, this is just wasted space */ + event->time_delta = 0; + event->array[0] = 0; + ret = 0; + } + + *delta = 0; + + return ret; +} + +static struct ring_buffer_event * +rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer, + unsigned type, unsigned long length) +{ + struct ring_buffer_event *event; + u64 ts, delta; + int commit = 0; + + again: + ts = ring_buffer_time_stamp(cpu_buffer->cpu); + + /* + * Only the first commit can update the timestamp. + * Yes there is a race here. If an interrupt comes in + * just after the conditional and it traces too, then it + * will also check the deltas. More than one timestamp may + * also be made. But only the entry that did the actual + * commit will be something other than zero. + */ + if (cpu_buffer->tail_page == cpu_buffer->commit_page && + rb_page_write(cpu_buffer->tail_page) == + rb_commit_index(cpu_buffer)) { + + delta = ts - cpu_buffer->write_stamp; + + /* make sure this delta is calculated here */ + barrier(); + + /* Did the write stamp get updated already? */ + if (unlikely(ts < cpu_buffer->write_stamp)) + goto again; + + if (test_time_stamp(delta)) { + + commit = rb_add_time_stamp(cpu_buffer, &ts, &delta); + + if (commit == -EBUSY) + return NULL; + + if (commit == -EAGAIN) + goto again; + + RB_WARN_ON(cpu_buffer, commit < 0); + } + } else + /* Non commits have zero deltas */ + delta = 0; + + event = __rb_reserve_next(cpu_buffer, type, length, &ts); + if (PTR_ERR(event) == -EAGAIN) + goto again; + + if (!event) { + if (unlikely(commit)) + /* + * Ouch! We needed a timestamp and it was commited. But + * we didn't get our event reserved. + */ + rb_set_commit_to_write(cpu_buffer); + return NULL; + } + + /* + * If the timestamp was commited, make the commit our entry + * now so that we will update it when needed. + */ + if (commit) + rb_set_commit_event(cpu_buffer, event); + else if (!rb_is_commit(cpu_buffer, event)) + delta = 0; + + event->time_delta = delta; + + return event; +} + +static DEFINE_PER_CPU(int, rb_need_resched); + +/** + * ring_buffer_lock_reserve - reserve a part of the buffer + * @buffer: the ring buffer to reserve from + * @length: the length of the data to reserve (excluding event header) + * @flags: a pointer to save the interrupt flags + * + * Returns a reseverd event on the ring buffer to copy directly to. + * The user of this interface will need to get the body to write into + * and can use the ring_buffer_event_data() interface. + * + * The length is the length of the data needed, not the event length + * which also includes the event header. + * + * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. + * If NULL is returned, then nothing has been allocated or locked. + */ +struct ring_buffer_event * +ring_buffer_lock_reserve(struct ring_buffer *buffer, + unsigned long length, + unsigned long *flags) +{ + struct ring_buffer_per_cpu *cpu_buffer; + struct ring_buffer_event *event; + int cpu, resched; + + if (atomic_read(&buffer->record_disabled)) + return NULL; + + /* If we are tracing schedule, we don't want to recurse */ + resched = need_resched(); + preempt_disable_notrace(); + + cpu = raw_smp_processor_id(); + + if (!cpu_isset(cpu, buffer->cpumask)) + goto out; + + cpu_buffer = buffer->buffers[cpu]; + + if (atomic_read(&cpu_buffer->record_disabled)) + goto out; + + length = rb_calculate_event_length(length); + if (length > BUF_PAGE_SIZE) + goto out; + + event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length); + if (!event) + goto out; + + /* + * Need to store resched state on this cpu. + * Only the first needs to. + */ + + if (preempt_count() == 1) + per_cpu(rb_need_resched, cpu) = resched; + + return event; + + out: + if (resched) + preempt_enable_notrace(); + else + preempt_enable_notrace(); + return NULL; +} + +static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, + struct ring_buffer_event *event) +{ + cpu_buffer->entries++; + + /* Only process further if we own the commit */ + if (!rb_is_commit(cpu_buffer, event)) + return; + + cpu_buffer->write_stamp += event->time_delta; + + rb_set_commit_to_write(cpu_buffer); +} + +/** + * ring_buffer_unlock_commit - commit a reserved + * @buffer: The buffer to commit to + * @event: The event pointer to commit. + * @flags: the interrupt flags received from ring_buffer_lock_reserve. + * + * This commits the data to the ring buffer, and releases any locks held. + * + * Must be paired with ring_buffer_lock_reserve. + */ +int ring_buffer_unlock_commit(struct ring_buffer *buffer, + struct ring_buffer_event *event, + unsigned long flags) +{ + struct ring_buffer_per_cpu *cpu_buffer; + int cpu = raw_smp_processor_id(); + + cpu_buffer = buffer->buffers[cpu]; + + rb_commit(cpu_buffer, event); + + /* + * Only the last preempt count needs to restore preemption. + */ + if (preempt_count() == 1) { + if (per_cpu(rb_need_resched, cpu)) + preempt_enable_no_resched_notrace(); + else + preempt_enable_notrace(); + } else + preempt_enable_no_resched_notrace(); + + return 0; +} + +/** + * ring_buffer_write - write data to the buffer without reserving + * @buffer: The ring buffer to write to. + * @length: The length of the data being written (excluding the event header) + * @data: The data to write to the buffer. + * + * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as + * one function. If you already have the data to write to the buffer, it + * may be easier to simply call this function. + * + * Note, like ring_buffer_lock_reserve, the length is the length of the data + * and not the length of the event which would hold the header. + */ +int ring_buffer_write(struct ring_buffer *buffer, + unsigned long length, + void *data) +{ + struct ring_buffer_per_cpu *cpu_buffer; + struct ring_buffer_event *event; + unsigned long event_length; + void *body; + int ret = -EBUSY; + int cpu, resched; + + if (atomic_read(&buffer->record_disabled)) + return -EBUSY; + + resched = need_resched(); + preempt_disable_notrace(); + + cpu = raw_smp_processor_id(); + + if (!cpu_isset(cpu, buffer->cpumask)) + goto out; + + cpu_buffer = buffer->buffers[cpu]; + + if (atomic_read(&cpu_buffer->record_disabled)) + goto out; + + event_length = rb_calculate_event_length(length); + event = rb_reserve_next_event(cpu_buffer, + RINGBUF_TYPE_DATA, event_length); + if (!event) + goto out; + + body = rb_event_data(event); + + memcpy(body, data, length); + + rb_commit(cpu_buffer, event); + + ret = 0; + out: + if (resched) + preempt_enable_no_resched_notrace(); + else + preempt_enable_notrace(); + + return ret; +} + +static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) +{ + struct buffer_page *reader = cpu_buffer->reader_page; + struct buffer_page *head = cpu_buffer->head_page; + struct buffer_page *commit = cpu_buffer->commit_page; + + return reader->read == rb_page_commit(reader) && + (commit == reader || + (commit == head && + head->read == rb_page_commit(commit))); +} + +/** + * ring_buffer_record_disable - stop all writes into the buffer + * @buffer: The ring buffer to stop writes to. + * + * This prevents all writes to the buffer. Any attempt to write + * to the buffer after this will fail and return NULL. + * + * The caller should call synchronize_sched() after this. + */ +void ring_buffer_record_disable(struct ring_buffer *buffer) +{ + atomic_inc(&buffer->record_disabled); +} + +/** + * ring_buffer_record_enable - enable writes to the buffer + * @buffer: The ring buffer to enable writes + * + * Note, multiple disables will need the same number of enables + * to truely enable the writing (much like preempt_disable). + */ +void ring_buffer_record_enable(struct ring_buffer *buffer) +{ + atomic_dec(&buffer->record_disabled); +} + +/** + * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer + * @buffer: The ring buffer to stop writes to. + * @cpu: The CPU buffer to stop + * + * This prevents all writes to the buffer. Any attempt to write + * to the buffer after this will fail and return NULL. + * + * The caller should call synchronize_sched() after this. + */ +void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + + if (!cpu_isset(cpu, buffer->cpumask)) + return; + + cpu_buffer = buffer->buffers[cpu]; + atomic_inc(&cpu_buffer->record_disabled); +} + +/** + * ring_buffer_record_enable_cpu - enable writes to the buffer + * @buffer: The ring buffer to enable writes + * @cpu: The CPU to enable. + * + * Note, multiple disables will need the same number of enables + * to truely enable the writing (much like preempt_disable). + */ +void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + + if (!cpu_isset(cpu, buffer->cpumask)) + return; + + cpu_buffer = buffer->buffers[cpu]; + atomic_dec(&cpu_buffer->record_disabled); +} + +/** + * ring_buffer_entries_cpu - get the number of entries in a cpu buffer + * @buffer: The ring buffer + * @cpu: The per CPU buffer to get the entries from. + */ +unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + + if (!cpu_isset(cpu, buffer->cpumask)) + return 0; + + cpu_buffer = buffer->buffers[cpu]; + return cpu_buffer->entries; +} + +/** + * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer + * @buffer: The ring buffer + * @cpu: The per CPU buffer to get the number of overruns from + */ +unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + + if (!cpu_isset(cpu, buffer->cpumask)) + return 0; + + cpu_buffer = buffer->buffers[cpu]; + return cpu_buffer->overrun; +} + +/** + * ring_buffer_entries - get the number of entries in a buffer + * @buffer: The ring buffer + * + * Returns the total number of entries in the ring buffer + * (all CPU entries) + */ +unsigned long ring_buffer_entries(struct ring_buffer *buffer) +{ + struct ring_buffer_per_cpu *cpu_buffer; + unsigned long entries = 0; + int cpu; + + /* if you care about this being correct, lock the buffer */ + for_each_buffer_cpu(buffer, cpu) { + cpu_buffer = buffer->buffers[cpu]; + entries += cpu_buffer->entries; + } + + return entries; +} + +/** + * ring_buffer_overrun_cpu - get the number of overruns in buffer + * @buffer: The ring buffer + * + * Returns the total number of overruns in the ring buffer + * (all CPU entries) + */ +unsigned long ring_buffer_overruns(struct ring_buffer *buffer) +{ + struct ring_buffer_per_cpu *cpu_buffer; + unsigned long overruns = 0; + int cpu; + + /* if you care about this being correct, lock the buffer */ + for_each_buffer_cpu(buffer, cpu) { + cpu_buffer = buffer->buffers[cpu]; + overruns += cpu_buffer->overrun; + } + + return overruns; +} + +/** + * ring_buffer_iter_reset - reset an iterator + * @iter: The iterator to reset + * + * Resets the iterator, so that it will start from the beginning + * again. + */ +void ring_buffer_iter_reset(struct ring_buffer_iter *iter) +{ + struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; + + /* Iterator usage is expected to have record disabled */ + if (list_empty(&cpu_buffer->reader_page->list)) { + iter->head_page = cpu_buffer->head_page; + iter->head = cpu_buffer->head_page->read; + } else { + iter->head_page = cpu_buffer->reader_page; + iter->head = cpu_buffer->reader_page->read; + } + if (iter->head) + iter->read_stamp = cpu_buffer->read_stamp; + else + iter->read_stamp = iter->head_page->time_stamp; +} + +/** + * ring_buffer_iter_empty - check if an iterator has no more to read + * @iter: The iterator to check + */ +int ring_buffer_iter_empty(struct ring_buffer_iter *iter) +{ + struct ring_buffer_per_cpu *cpu_buffer; + + cpu_buffer = iter->cpu_buffer; + + return iter->head_page == cpu_buffer->commit_page && + iter->head == rb_commit_index(cpu_buffer); +} + +static void +rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, + struct ring_buffer_event *event) +{ + u64 delta; + + switch (event->type) { + case RINGBUF_TYPE_PADDING: + return; + + case RINGBUF_TYPE_TIME_EXTEND: + delta = event->array[0]; + delta <<= TS_SHIFT; + delta += event->time_delta; + cpu_buffer->read_stamp += delta; + return; + + case RINGBUF_TYPE_TIME_STAMP: + /* FIXME: not implemented */ + return; + + case RINGBUF_TYPE_DATA: + cpu_buffer->read_stamp += event->time_delta; + return; + + default: + BUG(); + } + return; +} + +static void +rb_update_iter_read_stamp(struct ring_buffer_iter *iter, + struct ring_buffer_event *event) +{ + u64 delta; + + switch (event->type) { + case RINGBUF_TYPE_PADDING: + return; + + case RINGBUF_TYPE_TIME_EXTEND: + delta = event->array[0]; + delta <<= TS_SHIFT; + delta += event->time_delta; + iter->read_stamp += delta; + return; + + case RINGBUF_TYPE_TIME_STAMP: + /* FIXME: not implemented */ + return; + + case RINGBUF_TYPE_DATA: + iter->read_stamp += event->time_delta; + return; + + default: + BUG(); + } + return; +} + +static struct buffer_page * +rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) +{ + struct buffer_page *reader = NULL; + unsigned long flags; + + spin_lock_irqsave(&cpu_buffer->lock, flags); + + again: + reader = cpu_buffer->reader_page; + + /* If there's more to read, return this page */ + if (cpu_buffer->reader_page->read < rb_page_size(reader)) + goto out; + + /* Never should we have an index greater than the size */ + RB_WARN_ON(cpu_buffer, + cpu_buffer->reader_page->read > rb_page_size(reader)); + + /* check if we caught up to the tail */ + reader = NULL; + if (cpu_buffer->commit_page == cpu_buffer->reader_page) + goto out; + + /* + * Splice the empty reader page into the list around the head. + * Reset the reader page to size zero. + */ + + reader = cpu_buffer->head_page; + cpu_buffer->reader_page->list.next = reader->list.next; + cpu_buffer->reader_page->list.prev = reader->list.prev; + + local_set(&cpu_buffer->reader_page->write, 0); + local_set(&cpu_buffer->reader_page->commit, 0); + + /* Make the reader page now replace the head */ + reader->list.prev->next = &cpu_buffer->reader_page->list; + reader->list.next->prev = &cpu_buffer->reader_page->list; + + /* + * If the tail is on the reader, then we must set the head + * to the inserted page, otherwise we set it one before. + */ + cpu_buffer->head_page = cpu_buffer->reader_page; + + if (cpu_buffer->commit_page != reader) + rb_inc_page(cpu_buffer, &cpu_buffer->head_page); + + /* Finally update the reader page to the new head */ + cpu_buffer->reader_page = reader; + rb_reset_reader_page(cpu_buffer); + + goto again; + + out: + spin_unlock_irqrestore(&cpu_buffer->lock, flags); + + return reader; +} + +static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) +{ + struct ring_buffer_event *event; + struct buffer_page *reader; + unsigned length; + + reader = rb_get_reader_page(cpu_buffer); + + /* This function should not be called when buffer is empty */ + BUG_ON(!reader); + + event = rb_reader_event(cpu_buffer); + + if (event->type == RINGBUF_TYPE_DATA) + cpu_buffer->entries--; + + rb_update_read_stamp(cpu_buffer, event); + + length = rb_event_length(event); + cpu_buffer->reader_page->read += length; +} + +static void rb_advance_iter(struct ring_buffer_iter *iter) +{ + struct ring_buffer *buffer; + struct ring_buffer_per_cpu *cpu_buffer; + struct ring_buffer_event *event; + unsigned length; + + cpu_buffer = iter->cpu_buffer; + buffer = cpu_buffer->buffer; + + /* + * Check if we are at the end of the buffer. + */ + if (iter->head >= rb_page_size(iter->head_page)) { + BUG_ON(iter->head_page == cpu_buffer->commit_page); + rb_inc_iter(iter); + return; + } + + event = rb_iter_head_event(iter); + + length = rb_event_length(event); + + /* + * This should not be called to advance the header if we are + * at the tail of the buffer. + */ + BUG_ON((iter->head_page == cpu_buffer->commit_page) && + (iter->head + length > rb_commit_index(cpu_buffer))); + + rb_update_iter_read_stamp(iter, event); + + iter->head += length; + + /* check for end of page padding */ + if ((iter->head >= rb_page_size(iter->head_page)) && + (iter->head_page != cpu_buffer->commit_page)) + rb_advance_iter(iter); +} + +/** + * ring_buffer_peek - peek at the next event to be read + * @buffer: The ring buffer to read + * @cpu: The cpu to peak at + * @ts: The timestamp counter of this event. + * + * This will return the event that will be read next, but does + * not consume the data. + */ +struct ring_buffer_event * +ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) +{ + struct ring_buffer_per_cpu *cpu_buffer; + struct ring_buffer_event *event; + struct buffer_page *reader; + + if (!cpu_isset(cpu, buffer->cpumask)) + return NULL; + + cpu_buffer = buffer->buffers[cpu]; + + again: + reader = rb_get_reader_page(cpu_buffer); + if (!reader) + return NULL; + + event = rb_reader_event(cpu_buffer); + + switch (event->type) { + case RINGBUF_TYPE_PADDING: + RB_WARN_ON(cpu_buffer, 1); + rb_advance_reader(cpu_buffer); + return NULL; + + case RINGBUF_TYPE_TIME_EXTEND: + /* Internal data, OK to advance */ + rb_advance_reader(cpu_buffer); + goto again; + + case RINGBUF_TYPE_TIME_STAMP: + /* FIXME: not implemented */ + rb_advance_reader(cpu_buffer); + goto again; + + case RINGBUF_TYPE_DATA: + if (ts) { + *ts = cpu_buffer->read_stamp + event->time_delta; + ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts); + } + return event; + + default: + BUG(); + } + + return NULL; +} + +/** + * ring_buffer_iter_peek - peek at the next event to be read + * @iter: The ring buffer iterator + * @ts: The timestamp counter of this event. + * + * This will return the event that will be read next, but does + * not increment the iterator. + */ +struct ring_buffer_event * +ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) +{ + struct ring_buffer *buffer; + struct ring_buffer_per_cpu *cpu_buffer; + struct ring_buffer_event *event; + + if (ring_buffer_iter_empty(iter)) + return NULL; + + cpu_buffer = iter->cpu_buffer; + buffer = cpu_buffer->buffer; + + again: + if (rb_per_cpu_empty(cpu_buffer)) + return NULL; + + event = rb_iter_head_event(iter); + + switch (event->type) { + case RINGBUF_TYPE_PADDING: + rb_inc_iter(iter); + goto again; + + case RINGBUF_TYPE_TIME_EXTEND: + /* Internal data, OK to advance */ + rb_advance_iter(iter); + goto again; + + case RINGBUF_TYPE_TIME_STAMP: + /* FIXME: not implemented */ + rb_advance_iter(iter); + goto again; + + case RINGBUF_TYPE_DATA: + if (ts) { + *ts = iter->read_stamp + event->time_delta; + ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts); + } + return event; + + default: + BUG(); + } + + return NULL; +} + +/** + * ring_buffer_consume - return an event and consume it + * @buffer: The ring buffer to get the next event from + * + * Returns the next event in the ring buffer, and that event is consumed. + * Meaning, that sequential reads will keep returning a different event, + * and eventually empty the ring buffer if the producer is slower. + */ +struct ring_buffer_event * +ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts) +{ + struct ring_buffer_per_cpu *cpu_buffer; + struct ring_buffer_event *event; + + if (!cpu_isset(cpu, buffer->cpumask)) + return NULL; + + event = ring_buffer_peek(buffer, cpu, ts); + if (!event) + return NULL; + + cpu_buffer = buffer->buffers[cpu]; + rb_advance_reader(cpu_buffer); + + return event; +} + +/** + * ring_buffer_read_start - start a non consuming read of the buffer + * @buffer: The ring buffer to read from + * @cpu: The cpu buffer to iterate over + * + * This starts up an iteration through the buffer. It also disables + * the recording to the buffer until the reading is finished. + * This prevents the reading from being corrupted. This is not + * a consuming read, so a producer is not expected. + * + * Must be paired with ring_buffer_finish. + */ +struct ring_buffer_iter * +ring_buffer_read_start(struct ring_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + struct ring_buffer_iter *iter; + unsigned long flags; + + if (!cpu_isset(cpu, buffer->cpumask)) + return NULL; + + iter = kmalloc(sizeof(*iter), GFP_KERNEL); + if (!iter) + return NULL; + + cpu_buffer = buffer->buffers[cpu]; + + iter->cpu_buffer = cpu_buffer; + + atomic_inc(&cpu_buffer->record_disabled); + synchronize_sched(); + + spin_lock_irqsave(&cpu_buffer->lock, flags); + ring_buffer_iter_reset(iter); + spin_unlock_irqrestore(&cpu_buffer->lock, flags); + + return iter; +} + +/** + * ring_buffer_finish - finish reading the iterator of the buffer + * @iter: The iterator retrieved by ring_buffer_start + * + * This re-enables the recording to the buffer, and frees the + * iterator. + */ +void +ring_buffer_read_finish(struct ring_buffer_iter *iter) +{ + struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; + + atomic_dec(&cpu_buffer->record_disabled); + kfree(iter); +} + +/** + * ring_buffer_read - read the next item in the ring buffer by the iterator + * @iter: The ring buffer iterator + * @ts: The time stamp of the event read. + * + * This reads the next event in the ring buffer and increments the iterator. + */ +struct ring_buffer_event * +ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts) +{ + struct ring_buffer_event *event; + + event = ring_buffer_iter_peek(iter, ts); + if (!event) + return NULL; + + rb_advance_iter(iter); + + return event; +} + +/** + * ring_buffer_size - return the size of the ring buffer (in bytes) + * @buffer: The ring buffer. + */ +unsigned long ring_buffer_size(struct ring_buffer *buffer) +{ + return BUF_PAGE_SIZE * buffer->pages; +} + +static void +rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) +{ + cpu_buffer->head_page + = list_entry(cpu_buffer->pages.next, struct buffer_page, list); + local_set(&cpu_buffer->head_page->write, 0); + local_set(&cpu_buffer->head_page->commit, 0); + + cpu_buffer->head_page->read = 0; + + cpu_buffer->tail_page = cpu_buffer->head_page; + cpu_buffer->commit_page = cpu_buffer->head_page; + + INIT_LIST_HEAD(&cpu_buffer->reader_page->list); + local_set(&cpu_buffer->reader_page->write, 0); + local_set(&cpu_buffer->reader_page->commit, 0); + cpu_buffer->reader_page->read = 0; + + cpu_buffer->overrun = 0; + cpu_buffer->entries = 0; +} + +/** + * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer + * @buffer: The ring buffer to reset a per cpu buffer of + * @cpu: The CPU buffer to be reset + */ +void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; + unsigned long flags; + + if (!cpu_isset(cpu, buffer->cpumask)) + return; + + spin_lock_irqsave(&cpu_buffer->lock, flags); + + rb_reset_cpu(cpu_buffer); + + spin_unlock_irqrestore(&cpu_buffer->lock, flags); +} + +/** + * ring_buffer_reset - reset a ring buffer + * @buffer: The ring buffer to reset all cpu buffers + */ +void ring_buffer_reset(struct ring_buffer *buffer) +{ + int cpu; + + for_each_buffer_cpu(buffer, cpu) + ring_buffer_reset_cpu(buffer, cpu); +} + +/** + * rind_buffer_empty - is the ring buffer empty? + * @buffer: The ring buffer to test + */ +int ring_buffer_empty(struct ring_buffer *buffer) +{ + struct ring_buffer_per_cpu *cpu_buffer; + int cpu; + + /* yes this is racy, but if you don't like the race, lock the buffer */ + for_each_buffer_cpu(buffer, cpu) { + cpu_buffer = buffer->buffers[cpu]; + if (!rb_per_cpu_empty(cpu_buffer)) + return 0; + } + return 1; +} + +/** + * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? + * @buffer: The ring buffer + * @cpu: The CPU buffer to test + */ +int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + + if (!cpu_isset(cpu, buffer->cpumask)) + return 1; + + cpu_buffer = buffer->buffers[cpu]; + return rb_per_cpu_empty(cpu_buffer); +} + +/** + * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers + * @buffer_a: One buffer to swap with + * @buffer_b: The other buffer to swap with + * + * This function is useful for tracers that want to take a "snapshot" + * of a CPU buffer and has another back up buffer lying around. + * it is expected that the tracer handles the cpu buffer not being + * used at the moment. + */ +int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, + struct ring_buffer *buffer_b, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer_a; + struct ring_buffer_per_cpu *cpu_buffer_b; + + if (!cpu_isset(cpu, buffer_a->cpumask) || + !cpu_isset(cpu, buffer_b->cpumask)) + return -EINVAL; + + /* At least make sure the two buffers are somewhat the same */ + if (buffer_a->size != buffer_b->size || + buffer_a->pages != buffer_b->pages) + return -EINVAL; + + cpu_buffer_a = buffer_a->buffers[cpu]; + cpu_buffer_b = buffer_b->buffers[cpu]; + + /* + * We can't do a synchronize_sched here because this + * function can be called in atomic context. + * Normally this will be called from the same CPU as cpu. + * If not it's up to the caller to protect this. + */ + atomic_inc(&cpu_buffer_a->record_disabled); + atomic_inc(&cpu_buffer_b->record_disabled); + + buffer_a->buffers[cpu] = cpu_buffer_b; + buffer_b->buffers[cpu] = cpu_buffer_a; + + cpu_buffer_b->buffer = buffer_a; + cpu_buffer_a->buffer = buffer_b; + + atomic_dec(&cpu_buffer_a->record_disabled); + atomic_dec(&cpu_buffer_b->record_disabled); + + return 0; +} + |