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Commit b7e00a6c authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
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ftrace: Add private data to ftrace_ops 



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: default avatarSteven Rostedt <rostedt@goodmis.org>
parent f1b21c9a

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;