doc/developer/marker-types.txt

   1
   2 #define MARK_TRAP 1
   3 #define _MARK_TRAP (1 << MARK_TRAP)
   4   Can generate a trap
   5
   6 #define MARK_PREEMPT 2
   7 #define _MARK_PREEMPT (1 << MARK_PREEMPT)
   8   Permits blocking calls within probe.
   9   How to deal with probe removal :
  10   Each site has its per cpu probe_exec counters. The sum of the signed values
  11   gives the number of executors. Operations inc/dec on those values are done
  12   within preempt disable so they can be done non atomically without risking
  13   to be corrupted by another CPU.
  14   1 - disable site and remove call
  15   2 - while sum of probe_exec counters != 0, sleep 50ms
  16       fail after 10 loops
  17         - if someone sleeps in here for a long time or waits for
  18           a busy ressource, removal may fail with -EBUSY.
  19
  20 site :
  21
  22 if (enable) {
  23         preempt_disable();
  24         probe_exec[smp_processor_id()]++;
  25         preempt_enable();
  26         handler();
  27         preempt_disable();
  28         probe_exec[smp_processor_id()]--;
  29         preempt_enable();
  30 }
  31
  32 #define MARK_RESCHED 3
  33 #define _MARK_RESCHED (1 << MARK_RESCHED)
  34   preempt_schedule() will be called by the marker.
  35
  36 #define MARK_PRINTK 4
  37 #define _MARK_PRINTK (1 << MARK_PRINTK)
  38   vprintk can be called in the probe/printk can be called as probe.
  39
  40 #define MARK_LOCK_SAFE
  41 #define _MARK_LOCK_SAFE (1 << MARK_LOCK_SAFE)
  42   It is completely safe to take a lock, disable irqs, softirqs, ... from this marker.
  43   If unset, checking the context must be done to insure no deadlock or recursive
  44   call will occur.
  45
  46 #define _MARK_DEFAULT (_MARK_TRAP | _MARK_RESCHED | _MARK_PRINTK)
  47
  48 #define MARK (format, args...) _MARK(MARK_DEFAULT, format, ## args)
  49
  50 ex. i386
  51 #define _MARK(opt, format, args...) \
  52 do { \
  53         if (opt & _MARK_TRAP) \
  54                 MARK(opt, format, ## args); \
  55         else \
  56                 GEN_MARK(opt, format, ## args); \
  57 } while (0)
  58
  59 ex. powerpc
  60 #define _MARK(opt, format, args...) MARK(opt, format, ## args);
  61
  62
  63 MARK(opt, format, ...) \
  64 static declare opt in struct; \
  65 if (enable) {
  66         preempt_disable();
  67         if (opt & _MARK_PREEMPT) {
  68                 probe_exec[smp_processor_id()]++;
  69                 if (opt & _MARK_RESCHED)
  70                         preempt_enable();
  71                 else
  72                         preempt_enable_no_resched();
  73         }
  74         handler();
  75         if (opt & _MARK_PREEMPT) {
  76                 preempt_disable();
  77                 probe_exec[smp_processor_id()]--;
  78         }
  79         if (opt & _MARK_RESCHED)
  80                 preempt_enable();
  81         else
  82                 preempt_enable_no_resched();
  83 }
  84
  85
  86