On Sat, Aug 31, 2013 at 01:11:19AM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rost...@goodmis.org>
>
> For the ftrace_ops that use RCU read locks, and can not be called by
> unsafe RCU functions (those outside of RCU tracking), have them not
> update the RCU unsafe function records when they are being registered
> or unregistered.
>
> The ftrace function records store a counter of all the ftrace_ops
> callbacks that are hooked to the function the record represents.
> As unsafe RCU functions do not call callbacks that do not specify
> that they do not use RCU, do not update those records.
>
> Cc: Jiri Olsa <jo...@redhat.com>
> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> Signed-off-by: Steven Rostedt <rost...@goodmis.org>
Acked-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> ---
> kernel/trace/ftrace.c | 19 +++++++++++++++++--
> 1 file changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 3750360..d61f431 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -1168,6 +1168,12 @@ static struct ftrace_page *ftrace_new_pgs;
> static struct ftrace_page *ftrace_pages_start;
> static struct ftrace_page *ftrace_pages;
>
> +/*
> + * Hash of functions that are not safe to be called by
> + * callbacks that use RCU read locks.
> + */
> +static struct ftrace_hash *ftrace_unsafe_rcu;
> +
> static bool ftrace_hash_empty(struct ftrace_hash *hash)
> {
> return !hash || !hash->count;
> @@ -1638,6 +1644,7 @@ static void __ftrace_hash_rec_update(struct ftrace_ops
> *ops,
> {
> struct ftrace_hash *hash;
> struct ftrace_hash *other_hash;
> + struct ftrace_hash *rcu_hash;
> struct ftrace_page *pg;
> struct dyn_ftrace *rec;
> int count = 0;
> @@ -1647,6 +1654,12 @@ static void __ftrace_hash_rec_update(struct ftrace_ops
> *ops,
> if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
> return;
>
> + /* Ignore rcu unsafe functions unless ops handles them */
> + if (ops->flags & FTRACE_OPS_FL_RCU_SAFE)
> + rcu_hash = NULL;
> + else
> + rcu_hash = ftrace_unsafe_rcu;
> +
> /*
> * In the filter_hash case:
> * If the count is zero, we update all records.
> @@ -1680,6 +1693,10 @@ static void __ftrace_hash_rec_update(struct ftrace_ops
> *ops,
> int in_hash = 0;
> int match = 0;
>
> + /* Ignore all in the rcu unsafe hash */
> + if (ftrace_lookup_ip(rcu_hash, rec->ip))
> + continue;
> +
> if (all) {
> /*
> * Only the filter_hash affects all records.
> @@ -4291,8 +4308,6 @@ struct notifier_block ftrace_module_exit_nb = {
> extern struct ftrace_func_finder *__start_ftrace_unsafe_rcu[];
> extern struct ftrace_func_finder *__stop_ftrace_unsafe_rcu[];
>
> -static struct ftrace_hash *ftrace_unsafe_rcu;
> -
> static void __init create_unsafe_rcu_hash(void)
> {
> struct ftrace_func_finder *finder;
> --
> 1.7.10.4
>
>
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