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OpenCloudOS-Kernel
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ring_buffer: fix ring_buffer_read_page() 

Impact: change API and init bpage when copy

ring_buffer_read_page()/rb_remove_entries() may be called for
a partially consumed page.

Add a parameter for rb_remove_entries() and make it update
cpu_buffer->entries correctly for partially consumed pages.

ring_buffer_read_page() now returns the offset to the next event.

Init the bpage's time_stamp when return value is 0.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
This commit is contained in:
Lai Jiangshan 2009-02-09 14:21:17 +08:00 committed by Steven Rostedt
parent b85fa01ed9
commit 667d241258
1 changed files with 20 additions and 13 deletions
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33
kernel/trace/ring_buffer.c
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@ -2332,13 +2332,14 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
static void rb_remove_entries(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_data_page *bpage)
struct buffer_data_page *bpage,
unsigned int offset)
{
struct ring_buffer_event *event;
unsigned long head;
__raw_spin_lock(&cpu_buffer->lock);
for (head = 0; head < local_read(&bpage->commit);
for (head = offset; head < local_read(&bpage->commit);
head += rb_event_length(event)) {
event = __rb_data_page_index(bpage, head);
@ -2410,8 +2411,8 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
* if (!rpage)
* return error;
* ret = ring_buffer_read_page(buffer, &rpage, cpu, 0);
* if (ret)
* process_page(rpage);
* if (ret >= 0)
* process_page(rpage, ret);
*
* When @full is set, the function will not return true unless
* the writer is off the reader page.
@ -2422,8 +2423,8 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
* responsible for that.
*
* Returns:
* 1 if data has been transferred
* 0 if no data has been transferred.
* >=0 if data has been transferred, returns the offset of consumed data.
* <0 if no data has been transferred.
*/
int ring_buffer_read_page(struct ring_buffer *buffer,
void **data_page, int cpu, int full)
@ -2432,7 +2433,8 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
struct ring_buffer_event *event;
struct buffer_data_page *bpage;
unsigned long flags;
int ret = 0;
unsigned int read;
int ret = -1;
if (!data_page)
return 0;
@ -2454,24 +2456,29 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
/* check for data */
if (!local_read(&cpu_buffer->reader_page->page->commit))
goto out;
read = cpu_buffer->reader_page->read;
/*
* If the writer is already off of the read page, then simply
* switch the read page with the given page. Otherwise
* we need to copy the data from the reader to the writer.
*/
if (cpu_buffer->reader_page == cpu_buffer->commit_page) {
unsigned int read = cpu_buffer->reader_page->read;
unsigned int commit = rb_page_commit(cpu_buffer->reader_page);
struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
if (full)
goto out;
/* The writer is still on the reader page, we must copy */
memcpy(bpage->data,
cpu_buffer->reader_page->page->data + read,
commit - read);
memcpy(bpage->data + read, rpage->data + read, commit - read);
/* consume what was read */
cpu_buffer->reader_page->read = commit;
/* update bpage */
local_set(&bpage->commit, commit);
if (!read)
bpage->time_stamp = rpage->time_stamp;
} else {
/* swap the pages */
rb_init_page(bpage);
@ -2480,10 +2487,10 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
cpu_buffer->reader_page->read = 0;
*data_page = bpage;
}
ret = 1;
ret = read;
/* update the entry counter */
rb_remove_entries(cpu_buffer, bpage);
rb_remove_entries(cpu_buffer, bpage, read);
out:
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);