#include <asm/local.h>
#include "trace.h"
+static void update_pages_handler(struct work_struct *work);
+
/*
* The ring buffer header is special. We must manually up keep it.
*/
/* ring buffer pages to update, > 0 to add, < 0 to remove */
int nr_pages_to_update;
struct list_head new_pages; /* new pages to add */
+ struct work_struct update_pages_work;
+ struct completion update_completion;
};
struct ring_buffer {
unsigned flags;
int cpus;
atomic_t record_disabled;
+ atomic_t resize_disabled;
cpumask_var_t cpumask;
struct lock_class_key *reader_lock_key;
raw_spin_lock_init(&cpu_buffer->reader_lock);
lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
+ INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
+ init_completion(&cpu_buffer->update_completion);
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
GFP_KERNEL, cpu_to_node(cpu));
static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
+static inline unsigned long rb_page_entries(struct buffer_page *bpage)
+{
+ return local_read(&bpage->entries) & RB_WRITE_MASK;
+}
+
+static inline unsigned long rb_page_write(struct buffer_page *bpage)
+{
+ return local_read(&bpage->write) & RB_WRITE_MASK;
+}
+
static void
-rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
+rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
{
- struct buffer_page *bpage;
- struct list_head *p;
- unsigned i;
+ struct list_head *tail_page, *to_remove, *next_page;
+ struct buffer_page *to_remove_page, *tmp_iter_page;
+ struct buffer_page *last_page, *first_page;
+ unsigned int nr_removed;
+ unsigned long head_bit;
+ int page_entries;
+
+ head_bit = 0;
raw_spin_lock_irq(&cpu_buffer->reader_lock);
- rb_head_page_deactivate(cpu_buffer);
+ atomic_inc(&cpu_buffer->record_disabled);
+ /*
+ * We don't race with the readers since we have acquired the reader
+ * lock. We also don't race with writers after disabling recording.
+ * This makes it easy to figure out the first and the last page to be
+ * removed from the list. We unlink all the pages in between including
+ * the first and last pages. This is done in a busy loop so that we
+ * lose the least number of traces.
+ * The pages are freed after we restart recording and unlock readers.
+ */
+ tail_page = &cpu_buffer->tail_page->list;
- for (i = 0; i < nr_pages; i++) {
- if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)))
- goto out;
- p = cpu_buffer->pages->next;
- bpage = list_entry(p, struct buffer_page, list);
- list_del_init(&bpage->list);
- free_buffer_page(bpage);
+ /*
+ * tail page might be on reader page, we remove the next page
+ * from the ring buffer
+ */
+ if (cpu_buffer->tail_page == cpu_buffer->reader_page)
+ tail_page = rb_list_head(tail_page->next);
+ to_remove = tail_page;
+
+ /* start of pages to remove */
+ first_page = list_entry(rb_list_head(to_remove->next),
+ struct buffer_page, list);
+
+ for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
+ to_remove = rb_list_head(to_remove)->next;
+ head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
}
- if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)))
- goto out;
- rb_reset_cpu(cpu_buffer);
- rb_check_pages(cpu_buffer);
+ next_page = rb_list_head(to_remove)->next;
-out:
+ /*
+ * Now we remove all pages between tail_page and next_page.
+ * Make sure that we have head_bit value preserved for the
+ * next page
+ */
+ tail_page->next = (struct list_head *)((unsigned long)next_page |
+ head_bit);
+ next_page = rb_list_head(next_page);
+ next_page->prev = tail_page;
+
+ /* make sure pages points to a valid page in the ring buffer */
+ cpu_buffer->pages = next_page;
+
+ /* update head page */
+ if (head_bit)
+ cpu_buffer->head_page = list_entry(next_page,
+ struct buffer_page, list);
+
+ /*
+ * change read pointer to make sure any read iterators reset
+ * themselves
+ */
+ cpu_buffer->read = 0;
+
+ /* pages are removed, resume tracing and then free the pages */
+ atomic_dec(&cpu_buffer->record_disabled);
raw_spin_unlock_irq(&cpu_buffer->reader_lock);
+
+ RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
+
+ /* last buffer page to remove */
+ last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
+ list);
+ tmp_iter_page = first_page;
+
+ do {
+ to_remove_page = tmp_iter_page;
+ rb_inc_page(cpu_buffer, &tmp_iter_page);
+
+ /* update the counters */
+ page_entries = rb_page_entries(to_remove_page);
+ if (page_entries) {
+ /*
+ * If something was added to this page, it was full
+ * since it is not the tail page. So we deduct the
+ * bytes consumed in ring buffer from here.
+ * No need to update overruns, since this page is
+ * deleted from ring buffer and its entries are
+ * already accounted for.
+ */
+ local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
+ }
+
+ /*
+ * We have already removed references to this list item, just
+ * free up the buffer_page and its page
+ */
+ free_buffer_page(to_remove_page);
+ nr_removed--;
+
+ } while (to_remove_page != last_page);
+
+ RB_WARN_ON(cpu_buffer, nr_removed);
}
static void
unsigned i;
raw_spin_lock_irq(&cpu_buffer->reader_lock);
+ /* stop the writers while inserting pages */
+ atomic_inc(&cpu_buffer->record_disabled);
rb_head_page_deactivate(cpu_buffer);
for (i = 0; i < nr_pages; i++) {
rb_check_pages(cpu_buffer);
out:
+ atomic_dec(&cpu_buffer->record_disabled);
raw_spin_unlock_irq(&cpu_buffer->reader_lock);
}
-static void update_pages_handler(struct ring_buffer_per_cpu *cpu_buffer)
+static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
{
if (cpu_buffer->nr_pages_to_update > 0)
rb_insert_pages(cpu_buffer, &cpu_buffer->new_pages,
cpu_buffer->nr_pages_to_update);
else
rb_remove_pages(cpu_buffer, -cpu_buffer->nr_pages_to_update);
+
cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
- /* reset this value */
- cpu_buffer->nr_pages_to_update = 0;
+}
+
+static void update_pages_handler(struct work_struct *work)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
+ struct ring_buffer_per_cpu, update_pages_work);
+ rb_update_pages(cpu_buffer);
+ complete(&cpu_buffer->update_completion);
}
/**
*
* Minimum size is 2 * BUF_PAGE_SIZE.
*
- * Returns -1 on failure.
+ * Returns 0 on success and < 0 on failure.
*/
int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
int cpu_id)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned nr_pages;
- int cpu;
+ int cpu, err = 0;
/*
* Always succeed at resizing a non-existent buffer:
if (size < BUF_PAGE_SIZE * 2)
size = BUF_PAGE_SIZE * 2;
- atomic_inc(&buffer->record_disabled);
+ nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
- /* Make sure all writers are done with this buffer. */
- synchronize_sched();
+ /*
+ * Don't succeed if resizing is disabled, as a reader might be
+ * manipulating the ring buffer and is expecting a sane state while
+ * this is true.
+ */
+ if (atomic_read(&buffer->resize_disabled))
+ return -EBUSY;
+ /* prevent another thread from changing buffer sizes */
mutex_lock(&buffer->mutex);
- get_online_cpus();
-
- nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
if (cpu_id == RING_BUFFER_ALL_CPUS) {
/* calculate the pages to update */
cpu_buffer->nr_pages_to_update = nr_pages -
cpu_buffer->nr_pages;
-
/*
* nothing more to do for removing pages or no update
*/
if (cpu_buffer->nr_pages_to_update <= 0)
continue;
-
/*
* to add pages, make sure all new pages can be
* allocated without receiving ENOMEM
*/
INIT_LIST_HEAD(&cpu_buffer->new_pages);
if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
- &cpu_buffer->new_pages, cpu))
+ &cpu_buffer->new_pages, cpu)) {
/* not enough memory for new pages */
- goto no_mem;
+ err = -ENOMEM;
+ goto out_err;
+ }
+ }
+
+ get_online_cpus();
+ /*
+ * Fire off all the required work handlers
+ * Look out for offline CPUs
+ */
+ for_each_buffer_cpu(buffer, cpu) {
+ cpu_buffer = buffer->buffers[cpu];
+ if (!cpu_buffer->nr_pages_to_update ||
+ !cpu_online(cpu))
+ continue;
+
+ schedule_work_on(cpu, &cpu_buffer->update_pages_work);
+ }
+ /*
+ * This loop is for the CPUs that are not online.
+ * We can't schedule anything on them, but it's not necessary
+ * since we can change their buffer sizes without any race.
+ */
+ for_each_buffer_cpu(buffer, cpu) {
+ cpu_buffer = buffer->buffers[cpu];
+ if (!cpu_buffer->nr_pages_to_update ||
+ cpu_online(cpu))
+ continue;
+
+ rb_update_pages(cpu_buffer);
}
/* wait for all the updates to complete */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
- if (cpu_buffer->nr_pages_to_update) {
- update_pages_handler(cpu_buffer);
- }
+ if (!cpu_buffer->nr_pages_to_update ||
+ !cpu_online(cpu))
+ continue;
+
+ wait_for_completion(&cpu_buffer->update_completion);
+ /* reset this value */
+ cpu_buffer->nr_pages_to_update = 0;
}
+
+ put_online_cpus();
} else {
cpu_buffer = buffer->buffers[cpu_id];
+
if (nr_pages == cpu_buffer->nr_pages)
goto out;
INIT_LIST_HEAD(&cpu_buffer->new_pages);
if (cpu_buffer->nr_pages_to_update > 0 &&
__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
- &cpu_buffer->new_pages, cpu_id))
- goto no_mem;
+ &cpu_buffer->new_pages, cpu_id)) {
+ err = -ENOMEM;
+ goto out_err;
+ }
- update_pages_handler(cpu_buffer);
+ get_online_cpus();
+
+ if (cpu_online(cpu_id)) {
+ schedule_work_on(cpu_id,
+ &cpu_buffer->update_pages_work);
+ wait_for_completion(&cpu_buffer->update_completion);
+ } else
+ rb_update_pages(cpu_buffer);
+
+ put_online_cpus();
+ /* reset this value */
+ cpu_buffer->nr_pages_to_update = 0;
}
out:
- put_online_cpus();
mutex_unlock(&buffer->mutex);
-
- atomic_dec(&buffer->record_disabled);
-
return size;
- no_mem:
+ out_err:
for_each_buffer_cpu(buffer, cpu) {
struct buffer_page *bpage, *tmp;
+
cpu_buffer = buffer->buffers[cpu];
- /* reset this number regardless */
cpu_buffer->nr_pages_to_update = 0;
+
if (list_empty(&cpu_buffer->new_pages))
continue;
+
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
}
- put_online_cpus();
mutex_unlock(&buffer->mutex);
- atomic_dec(&buffer->record_disabled);
- return -ENOMEM;
+ return err;
}
EXPORT_SYMBOL_GPL(ring_buffer_resize);
return __rb_page_index(iter->head_page, iter->head);
}
-static inline unsigned long rb_page_write(struct buffer_page *bpage)
-{
- return local_read(&bpage->write) & RB_WRITE_MASK;
-}
-
static inline unsigned rb_page_commit(struct buffer_page *bpage)
{
return local_read(&bpage->page->commit);
}
-static inline unsigned long rb_page_entries(struct buffer_page *bpage)
-{
- return local_read(&bpage->entries) & RB_WRITE_MASK;
-}
-
/* Size is determined by what has been committed */
static inline unsigned rb_page_size(struct buffer_page *bpage)
{
iter->cpu_buffer = cpu_buffer;
+ atomic_inc(&buffer->resize_disabled);
atomic_inc(&cpu_buffer->record_disabled);
return iter;
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
atomic_dec(&cpu_buffer->record_disabled);
+ atomic_dec(&cpu_buffer->buffer->resize_disabled);
kfree(iter);
}
EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return;
+ atomic_inc(&buffer->resize_disabled);
atomic_inc(&cpu_buffer->record_disabled);
+ /* Make sure all commits have finished */
+ synchronize_sched();
+
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
atomic_dec(&cpu_buffer->record_disabled);
+ atomic_dec(&buffer->resize_disabled);
}
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
projects / users / hch / configfs.git / commitdiff