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- Do not update shortest_full in rb_watermark_hit() if the watermark is hit. The shortest_full field was being updated regardless if the task was going to wait or not. If the watermark is hit, then the task is not going to wait, so do not update the shortest_full field (used by the waker). - Update shortest_full field before setting the full_waiters_pending flag In the poll logic, the full_waiters_pending flag was being set before the shortest_full field was set. If the full_waiters_pending flag is set, writers will check the shortest_full field which has the least percentage of data that the ring buffer needs to be filled before waking up. The writer will check shortest_full if full_waiters_pending is set, and if the ring buffer percentage filled is greater than shortest full, then it will call the irq_work to wake up the waiters. The problem was that the poll logic set the full_waiters_pending flag before updating shortest_full, which when zero will always trigger the writer to call the irq_work to wake up the waiters. The irq_work will reset the shortest_full field back to zero as the woken waiters is suppose to reset it. - There's some optimized logic in the rb_watermark_hit() that is used in ring_buffer_wait(). Use that helper function in the poll logic as well. - Restructure ring_buffer_wait() to use wait_event_interruptible() The logic to wake up pending readers when the file descriptor is closed is racy. Restructure ring_buffer_wait() to allow callers to pass in conditions besides the ring buffer having enough data in it by using wait_event_interruptible(). - Update the tracing_wait_on_pipe() to call ring_buffer_wait() with its own conditions to exit the wait loop. -----BEGIN PGP SIGNATURE----- iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCZfH6MRQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qtlwAP9ZoSIkvw2MVu7FclgAguaX2CaylGEw sv0wZaCy1kgAPgD8CFhezZcHrt/RwJibpMxVnUs+DDqYnGdJsHYLihlbWgg= =99FG -----END PGP SIGNATURE----- Merge tag 'trace-ring-buffer-v6.8-rc7-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing updates from Steven Rostedt: - Do not update shortest_full in rb_watermark_hit() if the watermark is hit. The shortest_full field was being updated regardless if the task was going to wait or not. If the watermark is hit, then the task is not going to wait, so do not update the shortest_full field (used by the waker). - Update shortest_full field before setting the full_waiters_pending flag In the poll logic, the full_waiters_pending flag was being set before the shortest_full field was set. If the full_waiters_pending flag is set, writers will check the shortest_full field which has the least percentage of data that the ring buffer needs to be filled before waking up. The writer will check shortest_full if full_waiters_pending is set, and if the ring buffer percentage filled is greater than shortest full, then it will call the irq_work to wake up the waiters. The problem was that the poll logic set the full_waiters_pending flag before updating shortest_full, which when zero will always trigger the writer to call the irq_work to wake up the waiters. The irq_work will reset the shortest_full field back to zero as the woken waiters is suppose to reset it. - There's some optimized logic in the rb_watermark_hit() that is used in ring_buffer_wait(). Use that helper function in the poll logic as well. - Restructure ring_buffer_wait() to use wait_event_interruptible() The logic to wake up pending readers when the file descriptor is closed is racy. Restructure ring_buffer_wait() to allow callers to pass in conditions besides the ring buffer having enough data in it by using wait_event_interruptible(). - Update the tracing_wait_on_pipe() to call ring_buffer_wait() with its own conditions to exit the wait loop. * tag 'trace-ring-buffer-v6.8-rc7-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing/ring-buffer: Fix wait_on_pipe() race ring-buffer: Use wait_event_interruptible() in ring_buffer_wait() ring-buffer: Reuse rb_watermark_hit() for the poll logic ring-buffer: Fix full_waiters_pending in poll ring-buffer: Do not set shortest_full when full target is hit |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the ReStructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.