ftrace: Add private data to ftrace_ops (b7e00a6c) · Commits · 戴 / test

Passing data to the function callback was originally done by adding the ftrace_ops in another structure, and using the container_of() to get the field. But this adds a bit more complexity than it is worth, and adding a simple .private field to ftrace_ops makes things a lot easier. But be warned, the .private data should not be freed once it is used unless the ftrace_ops itself has gone through the necessary freeing routines. A simple synchronize_sched() is not enough as functions can be traced that are called outside the view of RCU and all its concoctions. Signed-off-by:

Steven Rostedt <rostedt@goodmis.org>

include/linux/ftrace.h

+12 −0

Original line number	Diff line number	Diff line
		@@ -105,11 +105,23 @@ enum {
		FTRACE_OPS_FL_INITIALIZED = 1 << 8,
		};

		/*
		* Note, ftrace_ops can be referenced outside of RCU protection.
		* (Although, for perf, the control ops prevent that). If ftrace_ops is
		* allocated and not part of kernel core data, the unregistering of it will
		* perform a scheduling on all CPUs to make sure that there are no more users.
		* Depending on the load of the system that may take a bit of time.
		*
		* Any private data added must also take care not to be freed and if private
		* data is added to a ftrace_ops that is in core code, the user of the
		* ftrace_ops must perform a schedule_on_each_cpu() before freeing it.
		*/
		struct ftrace_ops {
		ftrace_func_t func;
		struct ftrace_ops *next;
		unsigned long flags;
		int __percpu *disabled;
		void *private;
		#ifdef CONFIG_DYNAMIC_FTRACE
		struct ftrace_hash *notrace_hash;
		struct ftrace_hash *filter_hash;

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