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ANDROID: ring-buffer: Fix ring_buffer_read_page for external writers

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No shortcut is possible for reading a page without removing it from
the ring-buffer. The reader needs to be moved and its timestamp
updated.

Bug: 249050813
Change-Id: I80fbc1e265500e419278346e2973df2488b7e8b3
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
This commit is contained in:
Vincent Donnefort
2023-02-22 15:48:04 +00:00
parent e80aeaf594
commit c8d86d177a
1 changed files with 10 additions and 16 deletions
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26
kernel/trace/ring_buffer.c
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@@ -5884,7 +5884,8 @@ int ring_buffer_read_page(struct trace_buffer *buffer,
* Otherwise, we can simply swap the page with the one passed in.
*/
if (read || (len < (commit - read)) ||
cpu_buffer->reader_page == cpu_buffer->commit_page) {
cpu_buffer->reader_page == cpu_buffer->commit_page ||
unlikely(has_ext_writer(buffer))) {
struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
unsigned int rpos = read;
unsigned int pos = 0;
@@ -5949,21 +5950,14 @@ int ring_buffer_read_page(struct trace_buffer *buffer,
cpu_buffer->read += rb_page_entries(reader);
cpu_buffer->read_bytes += BUF_PAGE_SIZE;
if (unlikely(has_ext_writer(buffer))) {
u64 commit = local_read(&reader->page->commit);
memcpy(bpage, reader->page,
BUF_PAGE_HDR_SIZE + commit);
} else {
/* swap the pages */
rb_init_page(bpage);
bpage = reader->page;
reader->page = *data_page;
local_set(&reader->write, 0);
local_set(&reader->entries, 0);
reader->read = 0;
*data_page = bpage;
}
/* swap the pages */
rb_init_page(bpage);
bpage = reader->page;
reader->page = *data_page;
local_set(&reader->write, 0);
local_set(&reader->entries, 0);
reader->read = 0;
*data_page = bpage;
/*
* Use the real_end for the data size,