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c1fa617cae
The TRACE_EVENT() macro handles dynamic strings by having:
TP_PROTO(struct some_struct *s),
TP_ARGS(s),
TP_STRUCT__entry(
__string(my_string, s->string)
),
TP_fast_assign(
__assign_str(my_string, s->string);
)
TP_printk("%s", __get_str(my_string))
There's even some code that may call a function helper to find the
s->string value. The problem with the above is that the work to get the
s->string is done twice. Once at the __string() and again in the
__assign_str().
But the __string() uses dynamic_array() which has a helper structure that
is created holding the offsets and length of the string fields. Instead of
finding the string twice, just save it off in another field from that
helper structure, and have __assign_str() use that instead.
Note, this also means that the second parameter of __assign_str() isn't
even used anymore, and may be removed in the future.
Link: https://lore.kernel.org/linux-trace-kernel/20240222211442.634192653@goodmis.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Chuck Lever <chuck.lever@oracle.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.