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Subject[for-next][PATCH 5/7] ftrace: Create separate t_func_next() to simplify the function / hash logic
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

I noticed that if I use dd to read the set_ftrace_filter file that the first
hash command is repeated.

# cd /sys/kernel/debug/tracing
# echo schedule > set_ftrace_filter
# echo do_IRQ >> set_ftrace_filter
# echo schedule:traceoff >> set_ftrace_filter
# echo do_IRQ:traceoff >> set_ftrace_filter

# cat set_ftrace_filter
schedule
do_IRQ
schedule:traceoff:unlimited
do_IRQ:traceoff:unlimited

# dd if=set_ftrace_filter bs=1
schedule
do_IRQ
schedule:traceoff:unlimited
schedule:traceoff:unlimited
do_IRQ:traceoff:unlimited
98+0 records in
98+0 records out
98 bytes copied, 0.00265011 s, 37.0 kB/s

This is due to the way t_start() calls t_next() as well as the seq_file
calls t_next() and the state is slightly different between the two. Namely,
t_start() will call t_next() with a local "pos" variable.

By separating out the function listing from t_next() into its own function,
we can have better control of outputting the functions and the hash of
triggers. This simplifies the code.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/ftrace.c | 45 +++++++++++++++++++++++++++++++--------------
1 file changed, 31 insertions(+), 14 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index d4b18ce9ba88..aff7a2c08387 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3154,22 +3154,12 @@ t_hash_show(struct seq_file *m, struct ftrace_iterator *iter)
}

static void *
-t_next(struct seq_file *m, void *v, loff_t *pos)
+t_func_next(struct seq_file *m, loff_t *pos)
{
struct ftrace_iterator *iter = m->private;
struct dyn_ftrace *rec = NULL;

- if (unlikely(ftrace_disabled))
- return NULL;
-
- if (iter->flags & FTRACE_ITER_HASH)
- return t_hash_next(m, pos);
-
(*pos)++;
- iter->pos = iter->func_pos = *pos;
-
- if (iter->flags & FTRACE_ITER_PRINTALL)
- return t_hash_start(m, pos);

retry:
if (iter->idx >= iter->pg->index) {
@@ -3192,13 +3182,40 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
}

if (!rec)
- return t_hash_start(m, pos);
+ return NULL;

+ iter->pos = iter->func_pos = *pos;
iter->func = rec;

return iter;
}

+static void *
+t_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ struct ftrace_iterator *iter = m->private;
+ void *ret;
+
+ if (unlikely(ftrace_disabled))
+ return NULL;
+
+ if (iter->flags & FTRACE_ITER_HASH)
+ return t_hash_next(m, pos);
+
+ if (iter->flags & FTRACE_ITER_PRINTALL) {
+ /* next must increment pos, and t_hash_start does not */
+ (*pos)++;
+ return t_hash_start(m, pos);
+ }
+
+ ret = t_func_next(m, pos);
+
+ if (!ret)
+ return t_hash_start(m, pos);
+
+ return ret;
+}
+
static void reset_iter_read(struct ftrace_iterator *iter)
{
iter->pos = 0;
@@ -3250,13 +3267,13 @@ static void *t_start(struct seq_file *m, loff_t *pos)
iter->pg = ftrace_pages_start;
iter->idx = 0;
for (l = 0; l <= *pos; ) {
- p = t_next(m, p, &l);
+ p = t_func_next(m, &l);
if (!p)
break;
}

if (!p)
- return NULL;
+ return t_hash_start(m, pos);

return iter;
}
--
2.10.2

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