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Linux kernel source tree
d50b07d05c
- Rewind persistent ring buffer on boot When the persistent ring buffer is being used for live kernel tracing and the system crashes, the tool that is reading the trace may not have recorded the data when the system crashed. Although the persistent ring buffer still has that data, when reading it after a reboot, it will start where it left off. That is, what was read will not be accessible. Instead, on reboot, have the persistent ring buffer restart where the data starts and this will allow the tooling to recover what was lost when the crash occurred. - Remove the ring_buffer_read_prepare_sync() logic Reading the trace file required stopping writing to the ring buffer as the trace file is only an iterator and does not consume what it read. It was originally not safe to read the ring buffer in this mode and required disabling writing. The ring_buffer_read_prepare_sync() logic was used to stop each per_cpu ring buffer, call synchronize_rcu() and then start the iterator. This was used instead of calling synchronize_rcu() for each per_cpu buffer. Today, the iterator has been updated where it is safe to read the trace file while writing to the ring buffer is still occurring. There is no more need to do this synchronization and it is causing large delays on machines with many CPUs. Remove this unneeded synchronization. - Make static string array a constant in show_irq_str() Making the string array into a constant has shown to decrease code text/data size. -----BEGIN PGP SIGNATURE----- iIoEABYKADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCaIkfURQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qnx4AQCNXOuKYJXDvXrkwf449agwrn0lCVyI vV0L65nyIrakpAD8COV/lw8DhlCpb/Lijlzzo5L0n9QpEElNpq5uEntNwgE= =1YIy -----END PGP SIGNATURE----- Merge tag 'trace-ringbuffer-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull ring-buffer updates from Steven Rostedt: - Rewind persistent ring buffer on boot When the persistent ring buffer is being used for live kernel tracing and the system crashes, the tool that is reading the trace may not have recorded the data when the system crashed. Although the persistent ring buffer still has that data, when reading it after a reboot, it will start where it left off. That is, what was read will not be accessible. Instead, on reboot, have the persistent ring buffer restart where the data starts and this will allow the tooling to recover what was lost when the crash occurred. - Remove the ring_buffer_read_prepare_sync() logic Reading the trace file required stopping writing to the ring buffer as the trace file is only an iterator and does not consume what it read. It was originally not safe to read the ring buffer in this mode and required disabling writing. The ring_buffer_read_prepare_sync() logic was used to stop each per_cpu ring buffer, call synchronize_rcu() and then start the iterator. This was used instead of calling synchronize_rcu() for each per_cpu buffer. Today, the iterator has been updated where it is safe to read the trace file while writing to the ring buffer is still occurring. There is no more need to do this synchronization and it is causing large delays on machines with many CPUs. Remove this unneeded synchronization. - Make static string array a constant in show_irq_str() Making the string array into a constant has shown to decrease code text/data size. * tag 'trace-ringbuffer-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Make the const read-only 'type' static ring-buffer: Remove ring_buffer_read_prepare_sync() tracing: ring_buffer: Rewind persistent ring buffer on reboot |
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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 reStructuredText 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.