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ftrace: Add private data to ftrace_ops

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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>
This commit is contained in:
Steven Rostedt (Red Hat) 2013-11-07 09:36:25 -05:00 committed by Steven Rostedt
parent f1b21c9a40
commit b7e00a6c53
1 changed files with 12 additions and 0 deletions
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12
include/linux/ftrace.h
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@ -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;