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3e46d910d8
poll() and select() on per_cpu trace_pipe and trace_pipe_raw do not work since kernel 6.1-rc6. This issue is seen after the commit42fb0a1e84("tracing/ring-buffer: Have polling block on watermark"). This issue is firstly detected and reported, when testing the CXL error events in the rasdaemon and also erified using the test application for poll() and select(). This issue occurs for the per_cpu case, when calling the ring_buffer_poll_wait(), in kernel/trace/ring_buffer.c, with the buffer_percent > 0 and then wait until the percentage of pages are available. The default value set for the buffer_percent is 50 in the kernel/trace/trace.c. As a fix, allow userspace application could set buffer_percent as 0 through the buffer_percent_fops, so that the task will wake up as soon as data is added to any of the specific cpu buffer. Link: https://lore.kernel.org/linux-trace-kernel/20230202182309.742-2-shiju.jose@huawei.com Cc: <mhiramat@kernel.org> Cc: <mchehab@kernel.org> Cc: <linux-edac@vger.kernel.org> Cc: stable@vger.kernel.org Fixes:42fb0a1e84("tracing/ring-buffer: Have polling block on watermark") Signed-off-by: Shiju Jose <shiju.jose@huawei.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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.