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Tracers can add specify options to modify them. This logic was added before instances were created and the tracer flags were global variables. After instances were created where a tracer may exist in more than one instance, the flags were not updated from being global into instance specific. This causes confusion with these options. For example, the function tracer has an option to enable function arguments: # cd /sys/kernel/tracing # mkdir instances/foo # echo function > instances/foo/current_tracer # echo 1 > options/func-args # echo function > current_tracer # cat trace [..] <idle>-0 [005] d..3. 1050.656187: rcu_needs_cpu() <-tick_nohz_next_event <idle>-0 [005] d..3. 1050.656188: get_next_timer_interrupt(basej=0x10002dbad, basem=0xf45fd7d300) <-tick_nohz_next_event <idle>-0 [005] d..3. 1050.656189: _raw_spin_lock(lock=0xffff8944bdf5de80) <-__get_next_timer_interrupt <idle>-0 [005] d..4. 1050.656190: do_raw_spin_lock(lock=0xffff8944bdf5de80) <-__get_next_timer_interrupt <idle>-0 [005] d..4. 1050.656191: _raw_spin_lock_nested(lock=0xffff8944bdf5f140, subclass=1) <-__get_next_timer_interrupt # cat instances/foo/options/func-args 1 # cat instances/foo/trace [..] kworker/4:1-88 [004] ...1. 298.127735: next_zone <-refresh_cpu_vm_stats kworker/4:1-88 [004] ...1. 298.127736: first_online_pgdat <-refresh_cpu_vm_stats kworker/4:1-88 [004] ...1. 298.127738: next_online_pgdat <-refresh_cpu_vm_stats kworker/4:1-88 [004] ...1. 298.127739: fold_diff <-refresh_cpu_vm_stats kworker/4:1-88 [004] ...1. 298.127741: round_jiffies_relative <-vmstat_update [..] The above shows that setting "func-args" in the top level instance also set it in the instance "foo", but since the interface of the trace flags are per instance, the update didn't take affect in the "foo" instance. Update the infrastructure to allow tracers to add a "default_flags" field in the tracer structure that can be set instead of "flags" which will make the flags per instance. If a tracer needs to keep the flags global (like blktrace), keeping the "flags" field set will keep the old behavior. This does not update function or the function graph tracers. That will be handled later. 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> Link: https://patch.msgid.link/20251111232429.305317942@kernel.org Fixes: f20a580627f43 ("ftrace: Allow instances to use function tracing") 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 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.