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Commit b04d52e3 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Steven Rostedt
Browse files

tracing/kprobes: Turn trace_probe->files into list_head 

I think that "ftrace_event_file *trace_probe[]" complicates the
code for no reason, turn it into list_head to simplify the code.
enable_trace_probe() no longer needs synchronize_sched().

This needs the extra sizeof(list_head) memory for every attached
ftrace_event_file, hopefully not a problem in this case.

Link: http://lkml.kernel.org/r/20130620173814.GA13165@redhat.com



Acked-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 3baa5e4c

kernel/trace/trace_kprobe.c

+37 −101
Original line number Diff line number Diff line
@@ -35,12 +35,17 @@ struct trace_probe { 
	const char		*symbol;	/* symbol name */

	struct ftrace_event_class	class;

	struct ftrace_event_call	call;

	struct ftrace_event_file * __rcu *files;

	struct list_head	files;

	ssize_t			size;		/* trace entry size */

	unsigned int		nr_args;

	struct probe_arg	args[];

};



struct event_file_link {

	struct ftrace_event_file	*file;

	struct list_head		list;

};



#define SIZEOF_TRACE_PROBE(n)			\

	(offsetof(struct trace_probe, args) +	\

	(sizeof(struct probe_arg) * (n)))
@@ -150,6 +155,7 @@ static struct trace_probe *alloc_trace_probe(const char *group, 
		goto error;



	INIT_LIST_HEAD(&tp->list);

	INIT_LIST_HEAD(&tp->files);

	return tp;

error:

	kfree(tp->call.name);
@@ -183,22 +189,6 @@ static struct trace_probe *find_trace_probe(const char *event, 
	return NULL;

}



/*

 * This and enable_trace_probe/disable_trace_probe rely on event_mutex

 * held by the caller, __ftrace_set_clr_event().

 */

static int trace_probe_nr_files(struct trace_probe *tp)

{

	struct ftrace_event_file **file = rcu_dereference_raw(tp->files);

	int ret = 0;



	if (file)

		while (*(file++))

			ret++;



	return ret;

}



/*

 * Enable trace_probe

 * if the file is NULL, enable "perf" handler, or enable "trace" handler.
@@ -209,29 +199,18 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) 
	int ret = 0;



	if (file) {

		struct ftrace_event_file **new, **old;

		int n = trace_probe_nr_files(tp);



		old = rcu_dereference_raw(tp->files);

		/* 1 is for new one and 1 is for stopper */

		new = kzalloc((n + 2) * sizeof(struct ftrace_event_file *),

			      GFP_KERNEL);

		if (!new) {

		struct event_file_link *link;



		link = kmalloc(sizeof(*link), GFP_KERNEL);

		if (!link) {

			ret = -ENOMEM;

			goto out;

		}

		memcpy(new, old, n * sizeof(struct ftrace_event_file *));

		new[n] = file;

		/* The last one keeps a NULL */



		rcu_assign_pointer(tp->files, new);

		tp->flags |= TP_FLAG_TRACE;

		link->file = file;

		list_add_tail_rcu(&link->list, &tp->files);



		if (old) {

			/* Make sure the probe is done with old files */

			synchronize_sched();

			kfree(old);

		}

		tp->flags |= TP_FLAG_TRACE;

	} else

		tp->flags |= TP_FLAG_PROFILE;
@@ -245,24 +224,16 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) 
	return ret;

}



static int

trace_probe_file_index(struct trace_probe *tp, struct ftrace_event_file *file)

static struct event_file_link *

find_event_file_link(struct trace_probe *tp, struct ftrace_event_file *file)

{

	struct ftrace_event_file **files;

	int i;

	struct event_file_link *link;



	/*

	 * Since all tp->files updater is protected by probe_enable_lock,

	 * we don't need to lock an rcu_read_lock.

	 */

	files = rcu_dereference_raw(tp->files);

	if (files) {

		for (i = 0; files[i]; i++)

			if (files[i] == file)

				return i;

	}

	list_for_each_entry(link, &tp->files, list)

		if (link->file == file)

			return link;



	return -1;

	return NULL;

}



/*
@@ -275,38 +246,23 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) 
	int ret = 0;



	if (file) {

		struct ftrace_event_file **new, **old;

		int n = trace_probe_nr_files(tp);

		int i, j;

		struct event_file_link *link;



		old = rcu_dereference_raw(tp->files);

		if (n == 0 || trace_probe_file_index(tp, file) < 0) {

		link = find_event_file_link(tp, file);

		if (!link) {

			ret = -EINVAL;

			goto out;

		}



		if (n == 1) {	/* Remove the last file */

			tp->flags &= ~TP_FLAG_TRACE;

			new = NULL;

		} else {

			new = kzalloc(n * sizeof(struct ftrace_event_file *),

				      GFP_KERNEL);

			if (!new) {

				ret = -ENOMEM;

				goto out;

			}



			/* This copy & check loop copies the NULL stopper too */

			for (i = 0, j = 0; j < n && i < n + 1; i++)

				if (old[i] != file)

					new[j++] = old[i];

		}

		list_del_rcu(&link->list);

		/* synchronize with kprobe_trace_func/kretprobe_trace_func */

		synchronize_sched();

		kfree(link);



		rcu_assign_pointer(tp->files, new);

		if (!list_empty(&tp->files))

			goto out;



		/* Make sure the probe is done with old files */

		synchronize_sched();

		kfree(old);

		tp->flags &= ~TP_FLAG_TRACE;

	} else

		tp->flags &= ~TP_FLAG_PROFILE;
@@ -871,20 +827,10 @@ __kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs, 
static __kprobes void

kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs)

{

	/*

	 * Note: preempt is already disabled around the kprobe handler.

	 * However, we still need an smp_read_barrier_depends() corresponding

	 * to smp_wmb() in rcu_assign_pointer() to access the pointer.

	 */

	struct ftrace_event_file **file = rcu_dereference_raw(tp->files);

	struct event_file_link *link;



	if (unlikely(!file))

		return;



	while (*file) {

		__kprobe_trace_func(tp, regs, *file);

		file++;

	}

	list_for_each_entry_rcu(link, &tp->files, list)

		__kprobe_trace_func(tp, regs, link->file);

}



/* Kretprobe handler */
@@ -931,20 +877,10 @@ static __kprobes void 
kretprobe_trace_func(struct trace_probe *tp, struct kretprobe_instance *ri,

		     struct pt_regs *regs)

{

	/*

	 * Note: preempt is already disabled around the kprobe handler.

	 * However, we still need an smp_read_barrier_depends() corresponding

	 * to smp_wmb() in rcu_assign_pointer() to access the pointer.

	 */

	struct ftrace_event_file **file = rcu_dereference_raw(tp->files);

	struct event_file_link *link;



	if (unlikely(!file))

		return;



	while (*file) {

		__kretprobe_trace_func(tp, ri, regs, *file);

		file++;

	}

	list_for_each_entry_rcu(link, &tp->files, list)

		__kretprobe_trace_func(tp, ri, regs, link->file);

}



/* Event entry printers */