diff options
| -rw-r--r-- | kernel/trace/ring_buffer.c | 487 |
1 files changed, 374 insertions, 113 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 09d4f0d879a..94af1fe56bb 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -116,8 +116,8 @@ void *ring_buffer_event_data(struct ring_buffer_event *event) */ struct buffer_page { u64 time_stamp; /* page time stamp */ - unsigned size; /* size of page data */ - unsigned write; /* index for next write */ + 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 */ @@ -157,6 +157,7 @@ struct ring_buffer_per_cpu { 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; @@ -185,12 +186,32 @@ struct ring_buffer_iter { u64 read_stamp; }; -#define RB_WARN_ON(buffer, cond) \ - if (unlikely(cond)) { \ - atomic_inc(&buffer->record_disabled); \ - WARN_ON(1); \ - return -1; \ - } +#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 @@ -204,22 +225,19 @@ 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(cpu_buffer, head->next->prev != head); - RB_WARN_ON(cpu_buffer, head->prev->next != head); + 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(cpu_buffer, page->list.next->prev != &page->list); - RB_WARN_ON(cpu_buffer, page->list.prev->next != &page->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 unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer) -{ - return cpu_buffer->head_page->size; -} - static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) { @@ -286,7 +304,6 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu) page->page = (void *)addr; INIT_LIST_HEAD(&cpu_buffer->reader_page->list); - cpu_buffer->reader_page->size = 0; ret = rb_allocate_pages(cpu_buffer, buffer->pages); if (ret < 0) @@ -294,8 +311,7 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu) cpu_buffer->head_page = list_entry(cpu_buffer->pages.next, struct buffer_page, list); - cpu_buffer->tail_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; @@ -563,15 +579,6 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) return -ENOMEM; } -static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) -{ - return cpu_buffer->reader_page->read == cpu_buffer->reader_page->size && - (cpu_buffer->tail_page == cpu_buffer->reader_page || - (cpu_buffer->tail_page == cpu_buffer->head_page && - cpu_buffer->head_page->read == - cpu_buffer->tail_page->write)); -} - static inline int rb_null_event(struct ring_buffer_event *event) { return event->type == RINGBUF_TYPE_PADDING; @@ -602,6 +609,33 @@ 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 @@ -637,16 +671,76 @@ static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, *page = list_entry(p, struct buffer_page, list); } -static inline void -rb_add_stamp(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts) +static inline unsigned +rb_event_index(struct ring_buffer_event *event) { - cpu_buffer->tail_page->time_stamp = *ts; - cpu_buffer->write_stamp = *ts; + unsigned long addr = (unsigned long)event; + + return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE); } -static void rb_reset_head_page(struct ring_buffer_per_cpu *cpu_buffer) +static inline int +rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer, + struct ring_buffer_event *event) { - cpu_buffer->head_page->read = 0; + 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) @@ -745,61 +839,120 @@ __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; + 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; - tail = cpu_buffer->tail_page->write; + write = local_add_return(length, &tail_page->write); + tail = write - length; - if (tail + length > BUF_PAGE_SIZE) { + /* 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(&cpu_buffer->lock); + 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 */ - WARN_ON(next_page == reader_page); + 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)) { - spin_unlock(&cpu_buffer->lock); - return NULL; + /* reset write */ + if (tail <= BUF_PAGE_SIZE) + local_set(&tail_page->write, tail); + goto out_unlock; } - /* count overflows */ - rb_update_overflow(cpu_buffer); + /* 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; + } + } - rb_inc_page(cpu_buffer, &head_page); - cpu_buffer->head_page = head_page; - rb_reset_head_page(cpu_buffer); + /* + * 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; } - if (tail != BUF_PAGE_SIZE) { + /* + * 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); - /* page padding */ event->type = RINGBUF_TYPE_PADDING; } - tail_page->size = tail; - tail_page = next_page; - tail_page->size = 0; - tail = 0; - cpu_buffer->tail_page = tail_page; - cpu_buffer->tail_page->write = tail; - rb_add_stamp(cpu_buffer, ts); - spin_unlock(&cpu_buffer->lock); + 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); } - BUG_ON(tail + length > BUF_PAGE_SIZE); + /* 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 @@ -808,6 +961,7 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer, { struct ring_buffer_event *event; static int once; + int ret; if (unlikely(*delta > (1ULL << 59) && !once++)) { printk(KERN_WARNING "Delta way too big! %llu" @@ -825,21 +979,38 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer, RB_LEN_TIME_EXTEND, ts); if (!event) - return -1; + return -EBUSY; - /* check to see if we went to the next page */ - if (cpu_buffer->tail_page->write) { - /* Still on same page, update timestamp */ - event->time_delta = *delta & TS_MASK; - event->array[0] = *delta >> TS_SHIFT; - /* commit the time event */ - cpu_buffer->tail_page->write += - rb_event_length(event); + 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; - *delta = 0; + /* 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; } - return 0; + *delta = 0; + + return ret; } static struct ring_buffer_event * @@ -848,32 +1019,69 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer, { struct ring_buffer_event *event; u64 ts, delta; + int commit = 0; + again: ts = ring_buffer_time_stamp(cpu_buffer->cpu); - if (cpu_buffer->tail_page->write) { + /* + * 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)) { - int ret; - ret = rb_add_time_stamp(cpu_buffer, &ts, &delta); - if (ret < 0) + 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 { - spin_lock(&cpu_buffer->lock); - rb_add_stamp(cpu_buffer, &ts); - spin_unlock(&cpu_buffer->lock); + } else + /* Non commits have zero deltas */ delta = 0; - } event = __rb_reserve_next(cpu_buffer, type, length, &ts); - if (!event) + 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 reserve went to the next page, our delta is zero */ - if (!cpu_buffer->tail_page->write) + /* + * 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; @@ -881,6 +1089,8 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer, 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 @@ -904,12 +1114,15 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer, { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; - int cpu; + int cpu, resched; if (atomic_read(&buffer->record_disabled)) return NULL; - local_irq_save(*flags); + /* 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)) @@ -922,26 +1135,42 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer, length = rb_calculate_event_length(length); if (length > BUF_PAGE_SIZE) - return NULL; + 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: - local_irq_restore(*flags); + 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->tail_page->write += rb_event_length(event); - cpu_buffer->tail_page->size = cpu_buffer->tail_page->write; - cpu_buffer->write_stamp += event->time_delta; 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); } /** @@ -965,7 +1194,16 @@ int ring_buffer_unlock_commit(struct ring_buffer *buffer, rb_commit(cpu_buffer, event); - local_irq_restore(flags); + /* + * 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; } @@ -989,15 +1227,17 @@ int ring_buffer_write(struct ring_buffer *buffer, { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; - unsigned long event_length, flags; + unsigned long event_length; void *body; int ret = -EBUSY; - int cpu; + int cpu, resched; if (atomic_read(&buffer->record_disabled)) return -EBUSY; - local_irq_save(flags); + resched = need_resched(); + preempt_disable_notrace(); + cpu = raw_smp_processor_id(); if (!cpu_isset(cpu, buffer->cpumask)) @@ -1022,11 +1262,26 @@ int ring_buffer_write(struct ring_buffer *buffer, ret = 0; out: - local_irq_restore(flags); + 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. @@ -1204,8 +1459,8 @@ int ring_buffer_iter_empty(struct ring_buffer_iter *iter) cpu_buffer = iter->cpu_buffer; - return iter->head_page == cpu_buffer->tail_page && - iter->head == cpu_buffer->tail_page->write; + return iter->head_page == cpu_buffer->commit_page && + iter->head == rb_commit_index(cpu_buffer); } static void @@ -1282,15 +1537,16 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) reader = cpu_buffer->reader_page; /* If there's more to read, return this page */ - if (cpu_buffer->reader_page->read < reader->size) + if (cpu_buffer->reader_page->read < rb_page_size(reader)) goto out; /* Never should we have an index greater than the size */ - WARN_ON(cpu_buffer->reader_page->read > reader->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->tail_page == cpu_buffer->reader_page) + if (cpu_buffer->commit_page == cpu_buffer->reader_page) goto out; /* @@ -1301,7 +1557,9 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) reader = cpu_buffer->head_page; cpu_buffer->reader_page->list.next = reader->list.next; cpu_buffer->reader_page->list.prev = reader->list.prev; - cpu_buffer->reader_page->size = 0; + + 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; @@ -1313,7 +1571,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) */ cpu_buffer->head_page = cpu_buffer->reader_page; - if (cpu_buffer->tail_page != reader) + if (cpu_buffer->commit_page != reader) rb_inc_page(cpu_buffer, &cpu_buffer->head_page); /* Finally update the reader page to the new head */ @@ -1363,8 +1621,8 @@ static void rb_advance_iter(struct ring_buffer_iter *iter) /* * Check if we are at the end of the buffer. */ - if (iter->head >= iter->head_page->size) { - BUG_ON(iter->head_page == cpu_buffer->tail_page); + if (iter->head >= rb_page_size(iter->head_page)) { + BUG_ON(iter->head_page == cpu_buffer->commit_page); rb_inc_iter(iter); return; } @@ -1377,16 +1635,16 @@ static void rb_advance_iter(struct ring_buffer_iter *iter) * 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->tail_page) && - (iter->head + length > cpu_buffer->tail_page->write)); + 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 >= iter->head_page->size) && - (iter->head_page != cpu_buffer->tail_page)) + if ((iter->head >= rb_page_size(iter->head_page)) && + (iter->head_page != cpu_buffer->commit_page)) rb_advance_iter(iter); } @@ -1420,7 +1678,7 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) switch (event->type) { case RINGBUF_TYPE_PADDING: - WARN_ON(1); + RB_WARN_ON(cpu_buffer, 1); rb_advance_reader(cpu_buffer); return NULL; @@ -1622,14 +1880,17 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) { cpu_buffer->head_page = list_entry(cpu_buffer->pages.next, struct buffer_page, list); - cpu_buffer->head_page->size = 0; - cpu_buffer->tail_page = cpu_buffer->head_page; - cpu_buffer->tail_page->size = 0; - INIT_LIST_HEAD(&cpu_buffer->reader_page->list); - cpu_buffer->reader_page->size = 0; + 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->write = 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; |