• Steven Rostedt (Red Hat)'s avatar
    tracepoint: Give priority to probes of tracepoints · 7904b5c4
    Steven Rostedt (Red Hat) authored
    In order to guarantee that a probe will be called before other probes that
    are attached to a tracepoint, there needs to be a mechanism to provide
    priority of one probe over the others.
    
    Adding a prio field to the struct tracepoint_func, which lets the probes be
    sorted by the priority set in the structure. If no priority is specified,
    then a priority of 10 is given (this is a macro, and perhaps may be changed
    in the future).
    
    Now probes may be added to affect other probes that are attached to a
    tracepoint with a guaranteed order.
    
    One use case would be to allow tracing of tracepoints be able to filter by
    pid. A special (higher priority probe) may be added to the sched_switch
    tracepoint and set the necessary flags of the other tracepoints to notify
    them if they should be traced or not. In case a tracepoint is enabled at the
    sched_switch tracepoint too, the order of the two are not random.
    
    Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    7904b5c4
tracepoint.c 14.5 KB