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ftrace: Fix indexing of t_hash_start() from t_next()

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t_hash_start() does not increment *pos, where as t_next() must. But when
t_next() does increment *pos, it must still pass in the original *pos to
t_hash_start() otherwise it will skip the first instance:

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

The above called t_hash_start() from t_start() as there was only one
function (call_rcu), but if we add another function:

 # echo xfrm_policy_destroy_rcu >> set_ftrace_filter
 # cat set_ftrace_filter
call_rcu
xfrm_policy_destroy_rcu
do_IRQ:traceoff:unlimited

The "schedule:traceoff" disappears.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2017-04-17 10:22:29 -04:00
parent acceb72e90
commit fcdc712579
1 changed files with 3 additions and 2 deletions
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5
kernel/trace/ftrace.c
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@ -3205,6 +3205,7 @@ static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
struct ftrace_iterator *iter = m->private;
loff_t l = *pos; /* t_hash_start() must use original pos */
void *ret;
if (unlikely(ftrace_disabled))
@ -3216,13 +3217,13 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
if (iter->flags & FTRACE_ITER_PRINTALL) {
/* next must increment pos, and t_hash_start does not */
(*pos)++;
return t_hash_start(m, pos);
return t_hash_start(m, &l);
}
ret = t_func_next(m, pos);
if (!ret)
return t_hash_start(m, pos);
return t_hash_start(m, &l);
return ret;
}