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ftrace: Don't manipulate @pos in t_start()

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It's rather confusing that in t_start(), in some cases @pos is
incremented, and in some cases it's decremented and then incremented.

This patch rewrites t_start() in a much more general way.

Thus we fix a bug that if ftrace_filtered == 1, functions have tracer
hooks won't be printed, because the branch is always unreachable:

static void *t_start(...)
{
	...
	if (!p)
		return t_hash_start(m, pos);
	return p;
}

Before:
  # echo 'sys_open' > /mnt/tracing/set_ftrace_filter
  # echo 'sys_write:traceon:4' >> /mnt/tracing/set_ftrace_filter
  sys_open

After:
  # echo 'sys_open' > /mnt/tracing/set_ftrace_filter
  # echo 'sys_write:traceon:4' >> /mnt/tracing/set_ftrace_filter
  sys_open
  sys_write:traceon:count=4

Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A41874B.4090507@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Li Zefan 2009-06-24 09:54:19 +08:00 committed by Ingo Molnar
parent 85951842a1
commit 694ce0a544
1 changed files with 8 additions and 11 deletions
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19
kernel/trace/ftrace.c
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@ -1467,8 +1467,6 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
iter->pg = iter->pg->next;
iter->idx = 0;
goto retry;
} else {
iter->idx = -1;
}
} else {
rec = &iter->pg->records[iter->idx++];
@ -1497,6 +1495,7 @@ static void *t_start(struct seq_file *m, loff_t *pos)
{
struct ftrace_iterator *iter = m->private;
void *p = NULL;
loff_t l;
mutex_lock(&ftrace_lock);
/*
@ -1508,23 +1507,21 @@ static void *t_start(struct seq_file *m, loff_t *pos)
if (*pos > 0)
return t_hash_start(m, pos);
iter->flags |= FTRACE_ITER_PRINTALL;
(*pos)++;
return iter;
}
if (iter->flags & FTRACE_ITER_HASH)
return t_hash_start(m, pos);
if (*pos > 0) {
if (iter->idx < 0)
return p;
(*pos)--;
iter->idx--;
iter->pg = ftrace_pages_start;
iter->idx = 0;
for (l = 0; l <= *pos; ) {
p = t_next(m, p, &l);
if (!p)
break;
}
p = t_next(m, p, pos);
if (!p)
if (!p && iter->flags & FTRACE_ITER_FILTER)
return t_hash_start(m, pos);
return p;