lkml.org 
[lkml]   [2011]   [Nov]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 4/9] ftrace: Add enable/disable ftrace_ops control interface
    On Mon, Nov 28, 2011 at 03:21:33PM -0500, Steven Rostedt wrote:
    >
    > >
    > > @@ -311,6 +321,9 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops)
    > > if (ret < 0)
    > > return ret;
    > >
    > > + if (ops->flags & FTRACE_OPS_FL_CONTROL)
    > > + jump_label_dec(&ftrace_ops_control);
    > > +
    > > if (ftrace_enabled)
    > > update_ftrace_function();
    > >
    > > @@ -3577,8 +3590,14 @@ ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip)
    > > preempt_disable_notrace();
    > > op = rcu_dereference_raw(ftrace_ops_list);
    > > while (op != &ftrace_list_end) {
    > > + if (static_branch(&ftrace_ops_control))
    >
    > Instead of doing a static_branch() here, which makes me really nervous,
    > because this is called in function trace context, which has some strict
    > rules of its own, and is probably prone to recursion, we could add
    > another "ops" similar to the global_ops.
    >
    > We could make a control_ops, and add all ops with the
    > FTRACE_OPS_FL_CONTROL flag set to it. And then this function will have
    > its own loop that it will check the disabled flag, for the ops
    > registered to it.
    >
    > This code doesn't need to be touched, we just add a layer of redirection
    > for control ops and it will solve the jump_label issue.

    sounds good, I'll make the change

    thanks,
    jirka

    >
    > -- Steve
    >
    > > + if ((op->flags & FTRACE_OPS_FL_CONTROL) &&
    > > + atomic_read(&op->disabled))
    > > + goto next;
    > > +
    > > if (ftrace_ops_test(op, ip))
    > > op->func(ip, parent_ip);
    > > + next:
    > > op = rcu_dereference_raw(op->next);
    > > };
    > > preempt_enable_notrace();
    >
    >


    \
     
     \ /
      Last update: 2011-11-29 11:11    [W:0.026 / U:61.524 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site