• Mathieu Desnoyers's avatar
    Linux Kernel Markers: support multiple probes · fb40bd78
    Mathieu Desnoyers authored
    RCU style multiple probes support for the Linux Kernel Markers.  Common case
    (one probe) is still fast and does not require dynamic allocation or a
    supplementary pointer dereference on the fast path.
    
    - Move preempt disable from the marker site to the callback.
    
    Since we now have an internal callback, move the preempt disable/enable to the
    callback instead of the marker site.
    
    Since the callback change is done asynchronously (passing from a handler that
    supports arguments to a handler that does not setup the arguments is no
    arguments are passed), we can safely update it even if it is outside the
    preempt disable section.
    
    - Move probe arm to probe connection. Now, a connected probe is automatically
      armed.
    
    Remove MARK_MAX_FORMAT_LEN, unused.
    
    This patch modifies the Linux Kernel Markers API : it removes the probe
    "arm/disarm" and changes the probe function prototype : it now expects a
    va_list * instead of a "...".
    
    If we want to have more than one probe connected to a marker at a given
    time (LTTng, or blktrace, ssytemtap) then we need this patch. Without it,
    connecting a second probe handler to a marker will fail.
    
    It allow us, for instance, to do interesting combinations :
    
    Do standard tracing with LTTng and, eventually, to compute statistics
    with SystemTAP, or to have a special trigger on an event that would call
    a systemtap script which would stop flight recorder tracing.
    Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Mike Mason <mmlnx@us.ibm.com>
    Cc: Dipankar Sarma <dipankar@in.ibm.com>
    Cc: David Smith <dsmith@redhat.com>
    Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
    Cc: "Frank Ch. Eigler" <fche@redhat.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    fb40bd78
marker.h 4.29 KB