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Filename : indent.stp
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/* <tapsetdescription>
 * The indent tapset provides functions to generate indented lines for
 * nested kinds of trace messages.  Each line contains a relative
 * timestamp, and the process name / pid.  The timestamp is as per
 * provided by the __indent_timestamp function, which by default
 * measures microseconds.
 * </tapsetdescription>
 */

@__private30 global _indent_counters, _indent_timestamps

@__private30 function _generic_indent_depth:long (idx, delta)
{
  # pre-increment for positive delta and post-decrement for negative delta
  x = _indent_counters[idx] + (delta > 0 ? delta : 0)
  _indent_counters[idx] += delta

  return (x>0 ? x-1 : 0)
}

@__private30 function _generic_indent (idx, desc, delta) 
{
  ts = __indent_timestamp ()
  if (! _indent_counters[idx]) _indent_timestamps[idx] = ts

  depth = _generic_indent_depth(idx, delta)

  return sprintf("%6d %s:%-*s", (ts - _indent_timestamps[idx]), desc, depth, "")
}

/**
 * sfunction thread_indent - returns an amount of space with the current task information
 *
 * @delta: the amount of space added/removed for each call
 *
 * Description: This function returns a string with appropriate
 * indentation for a thread. Call it with a small positive or
 * matching negative delta. If this is the real outermost,
 * initial level of indentation, then the function resets the 
 * relative timestamp base to zero.  The timestamp is as per
 * provided by the __indent_timestamp function, which by default
 * measures microseconds.
 */
function thread_indent:string (delta:long)
{
  return _generic_indent (tid(), sprintf("%s(%d)", execname(), tid()), delta)
}

/**
 * sfunction thread_indent_depth - returns the nested-depth of the current task
 *
 * @delta: the amount of depth added/removed for each call
 *
 * Description: This function returns an integer equal to the nested
 * function-call depth starting from the outermost initial level. This function
 * is useful for saving space (consumed by whitespace) in traces with long
 * nested function calls. Use this function in a similar fashion to
 * thread_indent(), i.e., in call-probe, use thread_indent_depth(1) and in
 * return-probe, use thread_indent_depth(-1)
 */
function thread_indent_depth:long (delta:long)
{
  return _generic_indent_depth (tid(), delta)
}

/**
 * sfunction indent - returns an amount of space to indent
 *
 * @delta: the amount of space added/removed for each call
 *
 * Description: This function returns a string with appropriate
 * indentation. Call it with a small positive or matching negative
 * delta. Unlike the thread_indent function, the indent does not
 * track individual indent values on a per thread basis.
 */
function indent:string (delta:long){
  return _generic_indent(-1, "",  delta)
}

/**
 * sfunction indent_depth - returns the global nested-depth
 *
 * @delta: the amount of depth added/removed for each call
 *
 * Description: This function returns a number for appropriate indentation,
 * similar to indent(). Call it with a small positive or matching negative
 * delta. Unlike the thread_indent_depth function, the indent does not track
 * individual indent values on a per thread basis.
 */
function indent_depth:long (delta:long)
{
  return _generic_indent_depth (-1, delta)
}

/* The following example uses thread_indent() to trace the functions
 * called in the drivers/usb/core kernel source. It prints a relative
 * timestamp and the name and ID of the current process, followed by 
 * the appropriate indent and the function name. Note that 
 * 'char' swapper(0) indicates the kernel is running in interrupt
 * context and there is no valid current process.
 *
 * probe kernel.function("*@drivers/usb/core/*") {
 * 	printf("%s -> %s\n, thread_indent(1), probefunc())
 * }
 * probe kernel.function("*@drivers/usb/core/*").return {
 * 	printf("%s <- %s\n", thread_indent(-1), probefunc())
 * }
 *
 * //This prints:
 *  0 swapper(0): -> usb_hcd_irq
 *  8 swapper(0): <- usb_hcd_irq
 *  0 swapper(0): -> usb_hcd_irq
 * 10 swapper(0):  -> usb_hcd_giveback_urb
 * 16 swapper(0):   -> urb_unlink
 * 22 swapper(0):   <- usb_unlink
 * 29 swapper(0):   -> usb_free_urb
 * 35 swapper(0):   <- usb_hcd_urb
 * 39 swapper(0):  <- usb_hcd_giveback_urb
 * 45 swapper(0): <- usb_hcd_irq
 *  0 usb-storage(1338): -> usb_submit_urb
 *  6 usb-storage(1338):  -> usb_hcd_submit_urb
 * 12 usb-storage(1338):   -> usb_get_urb
 * 18 usb-storage(1338):   <- usb_get_urb
 * 25 usb-storage(1338):  <- usb_hcd_submit_urb
 * 29 usb-storage(1338): -> usb_submit_urb
 *  0 swapper(0): -> usb_hcd_irq
 *  7 swapper(0): <- usb_hcd_irq
 */