• Steven Rostedt (Red Hat)'s avatar
    ftrace: Allow no regs if no more callbacks require it · 4fbb48cb
    Steven Rostedt (Red Hat) authored
    When registering a function callback for the function tracer, the ops
    can specify if it wants to save full regs (like an interrupt would)
    for each function that it traces, or if it does not care about regs
    and just wants to have the fastest return possible.
    Once a ops has registered a function, if other ops register that
    function they all will receive the regs too. That's because it does
    the work once, it does it for everyone.
    Now if the ops wanting regs unregisters the function so that there's
    only ops left that do not care about regs, those ops will still
    continue getting regs and going through the work for it on that
    function. This is because the disabling of the rec counter only
    sees the ops registered, and does not see the ops that are still
    attached, and does not know if the current ops that are still attached
    want regs or not. To play it safe, it just keeps regs being processed
    until no function is registered anymore.
    Instead of doing that, check the ops that are still registered for that
    function and if none want regs for it anymore, then disable the
    processing of regs.
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>