Implements per-cpu-local iterator and channel-wide iterator. Implements a read() file operation based on these iterators. These iterators or the read() file operation can be used by ring buffer clients.
The channel-wide iterator implements timestamp-ordered fusion merge of per-cpu channels using a priority heap. Signed-off-by: Mathieu Desnoyers <[email protected]> --- include/linux/ringbuffer/iterator.h | 70 ++ lib/ringbuffer/Makefile | 1 lib/ringbuffer/ring_buffer_iterator.c | 796 ++++++++++++++++++++++++++++++++++ 3 files changed, 867 insertions(+) Index: linux.trees.git/lib/ringbuffer/ring_buffer_iterator.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux.trees.git/lib/ringbuffer/ring_buffer_iterator.c 2010-08-17 12:53:17.000000000 -0400 @@ -0,0 +1,796 @@ +/* + * ring_buffer_iterator.c + * + * (C) Copyright 2010 - Mathieu Desnoyers <[email protected]> + * + * Ring buffer and channel iterators. Get each event of a channel in order. Uses + * a prio heap for per-cpu buffers, giving a O(log(NR_CPUS)) algorithmic + * complexity for the "get next event" operation. + * + * Author: + * Mathieu Desnoyers <[email protected]> + * + * Dual LGPL v2.1/GPL v2 license. + */ + +#include <linux/ringbuffer/iterator.h> +#include <linux/jiffies.h> +#include <linux/module.h> + +/* + * Safety factor taking into account internal kernel interrupt latency. + * Assuming 250ms worse-case latency. + */ +#define MAX_SYSTEM_LATENCY 250 + +/* + * Maximum delta expected between trace clocks. At most 1 jiffy delta. + */ +#define MAX_CLOCK_DELTA (jiffies_to_usecs(1) * 1000) + +/** + * ring_buffer_get_next_record - Get the next record in a buffer. + * @chan: channel + * @buf: buffer + * + * Returns the size of the event read, -EAGAIN if buffer is empty, -ENODATA if + * buffer is empty and finalized. The buffer must already be opened for reading. + */ +ssize_t ring_buffer_get_next_record(struct channel *chan, + struct ring_buffer *buf) +{ + const struct ring_buffer_config *config = chan->backend.config; + struct ring_buffer_iter *iter = &buf->iter; + int ret; + +restart: + switch (iter->state) { + case ITER_GET_SUBBUF: + ret = ring_buffer_get_next_subbuf(buf); + if (ret && !ACCESS_ONCE(buf->finalized) + && config->alloc == RING_BUFFER_ALLOC_GLOBAL) { + /* + * Use "pull" scheme for global buffers. The reader + * itself flushes the buffer to "pull" data not visible + * to readers yet. Flush current subbuffer and re-try. + * + * Per-CPU buffers rather use a "push" scheme because + * the IPI needed to flush all CPU's buffers is too + * costly. In the "push" scheme, the reader waits for + * the writer periodic deferrable timer to flush the + * buffers (keeping track of a quiescent state + * timestamp). Therefore, the writer "pushes" data out + * of the buffers rather than letting the reader "pull" + * data from the buffer. + */ + ring_buffer_switch_slow(buf, SWITCH_ACTIVE); + ret = ring_buffer_get_next_subbuf(buf); + } + if (ret) + return ret; + iter->consumed = buf->cons_snapshot; + iter->data_size = ring_buffer_get_read_data_size(config, buf); + iter->read_offset = iter->consumed; + /* skip header */ + iter->read_offset += config->cb.subbuffer_header_size(); + iter->state = ITER_TEST_RECORD; + goto restart; + case ITER_TEST_RECORD: + if (iter->read_offset - iter->consumed >= iter->data_size) { + iter->state = ITER_PUT_SUBBUF; + } else { + CHAN_WARN_ON(chan, !config->cb.record_get); + config->cb.record_get(config, chan, buf, + iter->read_offset, + &iter->header_len, + &iter->payload_len, + &iter->timestamp); + iter->read_offset += iter->header_len; + subbuffer_consume_record(config, &buf->backend); + iter->state = ITER_NEXT_RECORD; + return iter->payload_len; + } + goto restart; + case ITER_NEXT_RECORD: + iter->read_offset += iter->payload_len; + iter->state = ITER_TEST_RECORD; + goto restart; + case ITER_PUT_SUBBUF: + ring_buffer_put_next_subbuf(buf); + iter->state = ITER_GET_SUBBUF; + goto restart; + default: + CHAN_WARN_ON(chan, 1); /* Should not happen */ + return -EPERM; + } +} +EXPORT_SYMBOL_GPL(ring_buffer_get_next_record); + +static int buf_is_higher(void *a, void *b) +{ + struct ring_buffer *bufa = a; + struct ring_buffer *bufb = b; + + /* Consider lowest timestamps to be at the top of the heap */ + return (bufa->iter.timestamp < bufb->iter.timestamp); +} + +static +void ring_buffer_get_empty_buf_records(const struct ring_buffer_config *config, + struct channel *chan) +{ + struct ptr_heap *heap = &chan->iter.heap; + struct ring_buffer *buf, *tmp; + ssize_t len; + + list_for_each_entry_safe(buf, tmp, &chan->iter.empty_head, + iter.empty_node) { + len = ring_buffer_get_next_record(chan, buf); + + /* + * Deal with -EAGAIN and -ENODATA. + * len >= 0 means record contains data. + * -EBUSY should never happen, because we support only one + * reader. + */ + switch (len) { + case -EAGAIN: + /* Keep node in empty list */ + break; + case -ENODATA: + /* + * Buffer is finalized. Don't add to list of empty + * buffer, because it has no more data to provide, ever. + */ + list_del(&buf->iter.empty_node); + break; + case -EBUSY: + CHAN_WARN_ON(chan, 1); + break; + default: + /* + * Insert buffer into the heap, remove from empty buffer + * list. The heap should never overflow. + */ + CHAN_WARN_ON(chan, len < 0); + list_del(&buf->iter.empty_node); + CHAN_WARN_ON(chan, heap_insert(heap, buf) != NULL); + } + } +} + +static +void ring_buffer_wait_for_qs(const struct ring_buffer_config *config, + struct channel *chan) +{ + u64 timestamp_qs; + unsigned long wait_msecs; + + /* + * No need to wait if no empty buffers are present. + */ + if (list_empty(&chan->iter.empty_head)) + return; + + timestamp_qs = config->cb.ring_buffer_clock_read(chan); + /* + * We need to consider previously empty buffers. + * Do a get next buf record on each of them. Add them to + * the heap if they have data. If at least one of them + * don't have data, we need to wait for + * switch_timer_interval + MAX_SYSTEM_LATENCY (so we are sure the + * buffers have been switched either by the timer or idle entry) and + * check them again, adding them if they have data. + */ + ring_buffer_get_empty_buf_records(config, chan); + + /* + * No need to wait if no empty buffers are present. + */ + if (list_empty(&chan->iter.empty_head)) + return; + + /* + * We need to wait for the buffer switch timer to run. If the + * CPU is idle, idle entry performed the switch. + * TODO: we could optimize further by skipping the sleep if all + * empty buffers belong to idle or offline cpus. + */ + wait_msecs = jiffies_to_msecs(chan->switch_timer_interval); + wait_msecs += MAX_SYSTEM_LATENCY; + msleep(wait_msecs); + ring_buffer_get_empty_buf_records(config, chan); + /* + * Any buffer still in the empty list here cannot possibly + * contain an event with a timestamp prior to "timestamp_qs". + * The new quiescent state timestamp is the one we grabbed + * before waiting for buffer data. It is therefore safe to + * ignore empty buffers up to last_qs timestamp for fusion + * merge. + */ + chan->iter.last_qs = timestamp_qs; +} + +/** + * channel_get_next_record - Get the next record in a channel. + * @chan: channel + * @ret_buf: the buffer in which the event is located (output) + * + * Returns the size of new current event, -EAGAIN if all buffers are empty, + * -ENODATA if all buffers are empty and finalized. The channel must already be + * opened for reading. + */ + +ssize_t channel_get_next_record(struct channel *chan, + struct ring_buffer **ret_buf) +{ + const struct ring_buffer_config *config = chan->backend.config; + struct ring_buffer *buf; + struct ptr_heap *heap; + ssize_t len; + + if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) { + *ret_buf = channel_get_ring_buffer(config, chan, 0); + return ring_buffer_get_next_record(chan, *ret_buf); + } + + heap = &chan->iter.heap; + + /* + * get next record for topmost buffer. + */ + buf = heap_maximum(heap); + if (buf) { + len = ring_buffer_get_next_record(chan, buf); + /* + * Deal with -EAGAIN and -ENODATA. + * len >= 0 means record contains data. + */ + switch (len) { + case -EAGAIN: + buf->iter.timestamp = 0; + list_add(&buf->iter.empty_node, &chan->iter.empty_head); + /* Remove topmost buffer from the heap */ + CHAN_WARN_ON(chan, heap_remove(heap) != buf); + break; + case -ENODATA: + /* + * Buffer is finalized. Remove buffer from heap and + * don't add to list of empty buffer, because it has no + * more data to provide, ever. + */ + CHAN_WARN_ON(chan, heap_remove(heap) != buf); + break; + case -EBUSY: + CHAN_WARN_ON(chan, 1); + break; + default: + /* + * Reinsert buffer into the heap. Note that heap can be + * partially empty, so we need to use + * heap_replace_max(). + */ + CHAN_WARN_ON(chan, len < 0); + CHAN_WARN_ON(chan, heap_replace_max(heap, buf) != buf); + break; + } + } + + buf = heap_maximum(heap); + if (!buf || buf->iter.timestamp > chan->iter.last_qs) { + /* + * Deal with buffers previously showing no data. + * Add buffers containing data to the heap, update + * last_qs. + */ + ring_buffer_wait_for_qs(config, chan); + } + + *ret_buf = buf = heap_maximum(heap); + if (buf) { + /* + * If this warning triggers, you probably need to check your + * system interrupt latency. Typical causes: too many printk() + * output going to a serial console with interrupts off. + * Allow for MAX_CLOCK_DELTA ns timestamp delta going backward. + * Observed on SMP KVM setups with trace_clock(). + */ + if (chan->iter.last_timestamp + > (buf->iter.timestamp + MAX_CLOCK_DELTA)) { + printk(KERN_WARNING "ring_buffer: timestamps going " + "backward. Last time %llu ns, cpu %d, " + "current time %llu ns, cpu %d, " + "delta %llu ns.\n", + chan->iter.last_timestamp, chan->iter.last_cpu, + buf->iter.timestamp, buf->backend.cpu, + chan->iter.last_timestamp - buf->iter.timestamp); + CHAN_WARN_ON(chan, 1); + } + chan->iter.last_timestamp = buf->iter.timestamp; + chan->iter.last_cpu = buf->backend.cpu; + return buf->iter.payload_len; + } else { + /* Heap is empty */ + if (list_empty(&chan->iter.empty_head)) + return -ENODATA; /* All buffers finalized */ + else + return -EAGAIN; /* Temporarily empty */ + } +} +EXPORT_SYMBOL_GPL(channel_get_next_record); + +static +void ring_buffer_iterator_init(struct channel *chan, struct ring_buffer *buf) +{ + if (buf->iter.allocated) + return; + + buf->iter.allocated = 1; + if (chan->iter.read_open && !buf->iter.read_open) { + CHAN_WARN_ON(chan, ring_buffer_open_read(buf) != 0); + buf->iter.read_open = 1; + } + + /* Add to list of buffers without any current record */ + if (chan->backend.config->alloc == RING_BUFFER_ALLOC_PER_CPU) + list_add(&buf->iter.empty_node, &chan->iter.empty_head); +} + +#ifdef CONFIG_HOTPLUG_CPU +static +int __cpuinit channel_iterator_cpu_hotplug(struct notifier_block *nb, + unsigned long action, + void *hcpu) +{ + unsigned int cpu = (unsigned long)hcpu; + struct channel *chan = container_of(nb, struct channel, + hp_iter_notifier); + struct ring_buffer *buf = per_cpu_ptr(chan->backend.buf, cpu); + const struct ring_buffer_config *config = chan->backend.config; + + if (!chan->hp_iter_enable) + return NOTIFY_DONE; + + CHAN_WARN_ON(chan, config->alloc == RING_BUFFER_ALLOC_GLOBAL); + + switch (action) { + case CPU_DOWN_FAILED: + case CPU_DOWN_FAILED_FROZEN: + case CPU_ONLINE: + case CPU_ONLINE_FROZEN: + ring_buffer_iterator_init(chan, buf); + return NOTIFY_OK; + default: + return NOTIFY_DONE; + } +} +#endif + +int channel_iterator_init(struct channel *chan) +{ + const struct ring_buffer_config *config = chan->backend.config; + struct ring_buffer *buf; + + if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { + int cpu, ret; + + INIT_LIST_HEAD(&chan->iter.empty_head); + ret = heap_init(&chan->iter.heap, + num_possible_cpus() + * sizeof(struct ring_buffer *), + GFP_KERNEL, buf_is_higher); + if (ret) + return ret; + /* + * In case of non-hotplug cpu, if the ring-buffer is allocated + * in early initcall, it will not be notified of secondary cpus. + * In that off case, we need to allocate for all possible cpus. + */ +#ifdef CONFIG_HOTPLUG_CPU + chan->hp_iter_notifier.notifier_call = + channel_iterator_cpu_hotplug; + chan->hp_iter_notifier.priority = 10; + register_cpu_notifier(&chan->hp_iter_notifier); + get_online_cpus(); + for_each_online_cpu(cpu) { + buf = per_cpu_ptr(chan->backend.buf, cpu); + ring_buffer_iterator_init(chan, buf); + } + chan->hp_iter_enable = 1; + put_online_cpus(); +#else + for_each_possible_cpu(cpu) { + buf = per_cpu_ptr(chan->backend.buf, cpu); + ring_buffer_iterator_init(chan, buf); + } +#endif + } else { + buf = channel_get_ring_buffer(config, chan, 0); + ring_buffer_iterator_init(chan, buf); + } + return 0; +} + +void channel_iterator_unregister_notifiers(struct channel *chan) +{ + const struct ring_buffer_config *config = chan->backend.config; + + if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { + chan->hp_iter_enable = 0; + unregister_cpu_notifier(&chan->hp_iter_notifier); + } +} + +void channel_iterator_free(struct channel *chan) +{ + const struct ring_buffer_config *config = chan->backend.config; + + if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) + heap_free(&chan->iter.heap); +} + +int ring_buffer_iterator_open(struct ring_buffer *buf) +{ + struct channel *chan = buf->backend.chan; + const struct ring_buffer_config *config = chan->backend.config; + CHAN_WARN_ON(chan, config->output != RING_BUFFER_ITERATOR); + return ring_buffer_open_read(buf); +} +EXPORT_SYMBOL_GPL(ring_buffer_iterator_open); + +/* + * Note: Iterators must not be mixed with other types of outputs, because an + * iterator can leave the buffer in "GET" state, which is not consistent with + * other types of output (mmap, splice, raw data read). + */ +void ring_buffer_iterator_release(struct ring_buffer *buf) +{ + ring_buffer_release_read(buf); +} +EXPORT_SYMBOL_GPL(ring_buffer_iterator_release); + +int channel_iterator_open(struct channel *chan) +{ + const struct ring_buffer_config *config = chan->backend.config; + struct ring_buffer *buf; + int ret = 0, cpu; + + CHAN_WARN_ON(chan, config->output != RING_BUFFER_ITERATOR); + + if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { + get_online_cpus(); + /* Allow CPU hotplug to keep track of opened reader */ + chan->iter.read_open = 1; + for_each_channel_cpu(cpu, chan) { + buf = channel_get_ring_buffer(config, chan, cpu); + ret = ring_buffer_iterator_open(buf); + if (ret) + goto error; + buf->iter.read_open = 1; + } + put_online_cpus(); + } else { + buf = channel_get_ring_buffer(config, chan, 0); + ret = ring_buffer_iterator_open(buf); + } + return ret; +error: + /* Error should always happen on CPU 0, hence no close is required. */ + CHAN_WARN_ON(chan, cpu != 0); + put_online_cpus(); + return ret; +} +EXPORT_SYMBOL_GPL(channel_iterator_open); + +void channel_iterator_release(struct channel *chan) +{ + const struct ring_buffer_config *config = chan->backend.config; + struct ring_buffer *buf; + int cpu; + + if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { + get_online_cpus(); + for_each_channel_cpu(cpu, chan) { + buf = channel_get_ring_buffer(config, chan, cpu); + if (buf->iter.read_open) { + ring_buffer_iterator_release(buf); + buf->iter.read_open = 0; + } + } + chan->iter.read_open = 0; + put_online_cpus(); + } else { + buf = channel_get_ring_buffer(config, chan, 0); + ring_buffer_iterator_release(buf); + } +} +EXPORT_SYMBOL_GPL(channel_iterator_release); + +void ring_buffer_iterator_reset(struct ring_buffer *buf) +{ + struct channel *chan = buf->backend.chan; + + if (buf->iter.state != ITER_GET_SUBBUF) + ring_buffer_put_next_subbuf(buf); + buf->iter.state = ITER_GET_SUBBUF; + /* Remove from heap (if present). */ + if (heap_cherrypick(&chan->iter.heap, buf)) + list_add(&buf->iter.empty_node, &chan->iter.empty_head); + buf->iter.timestamp = 0; + buf->iter.header_len = 0; + buf->iter.payload_len = 0; + buf->iter.consumed = 0; + buf->iter.read_offset = 0; + buf->iter.data_size = 0; + /* Don't reset allocated and read_open */ +} + +void channel_iterator_reset(struct channel *chan) +{ + const struct ring_buffer_config *config = chan->backend.config; + struct ring_buffer *buf; + int cpu; + + /* Empty heap, put into empty_head */ + while ((buf = heap_remove(&chan->iter.heap)) != NULL) + list_add(&buf->iter.empty_node, &chan->iter.empty_head); + + for_each_channel_cpu(cpu, chan) { + buf = channel_get_ring_buffer(config, chan, cpu); + ring_buffer_iterator_reset(buf); + } + /* Don't reset read_open */ + chan->iter.last_qs = 0; + chan->iter.last_timestamp = 0; + chan->iter.last_cpu = 0; + chan->iter.len_left = 0; +} + +/* + * Ring buffer payload extraction read() implementation. + */ +static +ssize_t channel_ring_buffer_file_read(struct file *filp, + char __user *user_buf, + size_t count, + loff_t *ppos, + struct channel *chan, + struct ring_buffer *buf, + int fusionmerge) +{ + const struct ring_buffer_config *config = chan->backend.config; + size_t read_count = 0, read_offset; + ssize_t len; + + might_sleep(); + if (!access_ok(VERIFY_WRITE, user_buf, count)) + return -EFAULT; + + /* Finish copy of previous record */ + if (*ppos != 0) { + if (read_count < count) { + len = chan->iter.len_left; + read_offset = *ppos; + if (config->alloc == RING_BUFFER_ALLOC_PER_CPU + && fusionmerge) + buf = heap_maximum(&chan->iter.heap); + CHAN_WARN_ON(chan, !buf); + goto skip_get_next; + } + } + + while (read_count < count) { + size_t copy_len, space_left; + + if (fusionmerge) + len = channel_get_next_record(chan, &buf); + else + len = ring_buffer_get_next_record(chan, buf); +len_test: + if (len < 0) { + /* + * Check if buffer is finalized (end of file). + */ + if (len == -ENODATA) { + /* A 0 read_count will tell about end of file */ + goto nodata; + } + if (filp->f_flags & O_NONBLOCK) { + if (!read_count) + read_count = -EAGAIN; + goto nodata; + } else { + int error; + + /* + * No data available at the moment, return what + * we got. + */ + if (read_count) + goto nodata; + + /* + * Wait for returned len to be >= 0 or -ENODATA. + */ + if (fusionmerge) + error = wait_event_interruptible( + chan->read_wait, + ((len = channel_get_next_record(chan, + &buf)), len != -EAGAIN)); + else + error = wait_event_interruptible( + buf->read_wait, + ((len = ring_buffer_get_next_record( + chan, buf)), len != -EAGAIN)); + CHAN_WARN_ON(chan, len == -EBUSY); + if (error) { + read_count = error; + goto nodata; + } + CHAN_WARN_ON(chan, len < 0 && len != -ENODATA); + goto len_test; + } + } + read_offset = buf->iter.read_offset; +skip_get_next: + space_left = count - read_count; + if (len <= space_left) { + copy_len = len; + chan->iter.len_left = 0; + *ppos = 0; + } else { + copy_len = space_left; + chan->iter.len_left = len - copy_len; + *ppos = read_offset + copy_len; + } + if (__ring_buffer_copy_to_user(&buf->backend, read_offset, + &user_buf[read_count], + copy_len)) { + /* + * Leave the len_left and ppos values at their current + * state, as we currently have a valid event to read. + */ + return -EFAULT; + } + read_count += copy_len; + }; + return read_count; + +nodata: + *ppos = 0; + chan->iter.len_left = 0; + return read_count; +} + +/** + * ring_buffer_sp_file_read - Read buffer record payload. + * @filp: file structure pointer. + * @buffer: user buffer to read data into. + * @count: number of bytes to read. + * @ppos: file read position. + * + * Returns a negative value on error, or the number of bytes read on success. + * ppos is used to save the position _within the current record_ between calls + * to read(). + */ +static +ssize_t ring_buffer_file_read(struct file *filp, + char __user *user_buf, + size_t count, + loff_t *ppos) +{ + struct inode *inode = filp->f_dentry->d_inode; + struct ring_buffer *buf = inode->i_private; + struct channel *chan = buf->backend.chan; + + return channel_ring_buffer_file_read(filp, user_buf, count, ppos, + chan, buf, 0); +} + +/** + * channel_file_read - Read channel record payload. + * @filp: file structure pointer. + * @buffer: user buffer to read data into. + * @count: number of bytes to read. + * @ppos: file read position. + * + * Returns a negative value on error, or the number of bytes read on success. + * ppos is used to save the position _within the current record_ between calls + * to read(). + */ +static +ssize_t channel_file_read(struct file *filp, + char __user *user_buf, + size_t count, + loff_t *ppos) +{ + struct inode *inode = filp->f_dentry->d_inode; + struct channel *chan = inode->i_private; + const struct ring_buffer_config *config = chan->backend.config; + + if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) + return channel_ring_buffer_file_read(filp, user_buf, count, + ppos, chan, NULL, 1); + else { + struct ring_buffer *buf = + channel_get_ring_buffer(config, chan, 0); + return channel_ring_buffer_file_read(filp, user_buf, count, + ppos, chan, buf, 0); + } +} + +static +int ring_buffer_file_open(struct inode *inode, struct file *file) +{ + struct ring_buffer *buf = inode->i_private; + int ret; + + ret = ring_buffer_iterator_open(buf); + if (ret) + return ret; + + file->private_data = buf; + ret = nonseekable_open(inode, file); + if (ret) + goto release_iter; + return 0; + +release_iter: + ring_buffer_iterator_release(buf); + return ret; +} + +static +int ring_buffer_file_release(struct inode *inode, struct file *file) +{ + struct ring_buffer *buf = inode->i_private; + + ring_buffer_iterator_release(buf); + return 0; +} + +static +int channel_file_open(struct inode *inode, struct file *file) +{ + struct channel *chan = inode->i_private; + int ret; + + ret = channel_iterator_open(chan); + if (ret) + return ret; + + file->private_data = chan; + ret = nonseekable_open(inode, file); + if (ret) + goto release_iter; + return 0; + +release_iter: + channel_iterator_release(chan); + return ret; +} + +static +int channel_file_release(struct inode *inode, struct file *file) +{ + struct channel *chan = inode->i_private; + + channel_iterator_release(chan); + return 0; +} + +const struct file_operations channel_payload_file_operations = { + .open = channel_file_open, + .release = channel_file_release, + .read = channel_file_read, + .llseek = ring_buffer_no_llseek, +}; +EXPORT_SYMBOL_GPL(channel_payload_file_operations); + +const struct file_operations ring_buffer_payload_file_operations = { + .open = ring_buffer_file_open, + .release = ring_buffer_file_release, + .read = ring_buffer_file_read, + .llseek = ring_buffer_no_llseek, +}; +EXPORT_SYMBOL_GPL(ring_buffer_payload_file_operations); Index: linux.trees.git/include/linux/ringbuffer/iterator.h =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux.trees.git/include/linux/ringbuffer/iterator.h 2010-08-16 16:09:23.000000000 -0400 @@ -0,0 +1,70 @@ +#ifndef _LINUX_RING_BUFFER_ITERATOR_H +#define _LINUX_RING_BUFFER_ITERATOR_H + +/* + * linux/ringbuffer/iterator.h + * + * (C) Copyright 2010 - Mathieu Desnoyers <[email protected]> + * + * Ring buffer and channel iterators. + * + * Author: + * Mathieu Desnoyers <[email protected]> + * + * Dual LGPL v2.1/GPL v2 license. + */ + +#include <linux/ringbuffer/backend.h> +#include <linux/ringbuffer/frontend.h> + +/* + * ring_buffer_get_next_record advances the buffer read position to the next + * record. It returns either the size of the next record, -EAGAIN if there is + * currently no data available, or -ENODATA if no data is available and buffer + * is finalized. + */ +extern ssize_t ring_buffer_get_next_record(struct channel *chan, + struct ring_buffer *buf); + +/* + * channel_get_next_record advances the buffer read position to the next record. + * It returns either the size of the next record, -EAGAIN if there is currently + * no data available, or -ENODATA if no data is available and buffer is + * finalized. + * Returns the current buffer in ret_buf. + */ +extern ssize_t channel_get_next_record(struct channel *chan, + struct ring_buffer **ret_buf); + +/** + * read_current_record - copy the buffer current record into dest. + * @buf: ring buffer + * @dest: destination where the record should be copied + * + * dest should be large enough to contain the record. Returns the number of + * bytes copied. + */ +static inline size_t read_current_record(struct ring_buffer *buf, void *dest) +{ + return ring_buffer_read(&buf->backend, buf->iter.read_offset, + dest, buf->iter.payload_len); +} + +extern int ring_buffer_iterator_open(struct ring_buffer *buf); +extern void ring_buffer_iterator_release(struct ring_buffer *buf); +extern int channel_iterator_open(struct channel *chan); +extern void channel_iterator_release(struct channel *chan); + +extern const struct file_operations channel_payload_file_operations; +extern const struct file_operations ring_buffer_payload_file_operations; + +/* + * Used internally. + */ +int channel_iterator_init(struct channel *chan); +void channel_iterator_unregister_notifiers(struct channel *chan); +void channel_iterator_free(struct channel *chan); +void channel_iterator_reset(struct channel *chan); +void ring_buffer_iterator_reset(struct ring_buffer *buf); + +#endif /* _LINUX_RING_BUFFER_ITERATOR_H */ Index: linux.trees.git/lib/ringbuffer/Makefile =================================================================== --- linux.trees.git.orig/lib/ringbuffer/Makefile 2010-08-16 16:09:23.000000000 -0400 +++ linux.trees.git/lib/ringbuffer/Makefile 2010-08-17 16:09:46.000000000 -0400 @@ -1,5 +1,6 @@ obj-y += ring_buffer_backend.o obj-y += ring_buffer_frontend.o +obj-y += ring_buffer_iterator.o obj-y += ring_buffer_vfs.o obj-y += ring_buffer_splice.o obj-y += ring_buffer_mmap.o _______________________________________________ ltt-dev mailing list [email protected] http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
