mono/metadata/lock-tracer.c

   1 /*
   2  * lock-tracer.c: Runtime simple lock tracer
   3  *
   4  * Authors:
   5  *      Rodrigo Kumpera (rkumpera@novell.com)
   6  *
   7  */
   8
   9 #include <config.h>
  10 #include <stdio.h>
  11 #include <string.h>
  12
  13 #include <sys/types.h>
  14 #include <unistd.h>
  15
  16 #ifdef HAVE_EXECINFO_H
  17 #include <execinfo.h>
  18 #endif
  19
  20 #include <mono/io-layer/io-layer.h>
  21
  22 #include "lock-tracer.h"
  23
  24 /*
  25  * This is a very simple lock trace implementation. It can be used to verify that the runtime is
  26  * correctly following all locking rules.
  27  *
  28  * To log more kind of locks just do the following:
  29  *      - add an entry into the RuntimeLocks enum
  30  *  - change EnterCriticalSection(mutex) to mono_locks_acquire (mutex, LockName)
  31  *  - change LeaveCriticalSection to mono_locks_release (mutex, LockName)
  32  *  - change the decoder to understand the new lock kind.
  33  *
  34  * TODO:
  35  *      - Use unbuffered IO without fsync
  36  *  - Switch to a binary log format
  37  *  - Enable tracing of more runtime locks
  38  *  - Add lock check assertions (must_not_hold_any_lock_but, must_hold_lock, etc)
  39  *   This should be used to verify methods that expect that a given lock is held at entrypoint, for example.
  40  *
  41  * To use the trace, define LOCK_TRACER in lock-trace.h and when running mono define MONO_ENABLE_LOCK_TRACER.
  42  * This will produce a locks.ZZZ where ZZZ is the pid of the mono process.
  43  * Use the decoder to verify the result.
  44  */
  45
  46 #ifdef LOCK_TRACER
  47
  48 static FILE *trace_file;
  49 static CRITICAL_SECTION tracer_lock;
  50
  51 typedef enum {
  52         RECORD_MUST_NOT_HOLD_ANY,
  53         RECORD_MUST_NOT_HOLD_ONE,
  54         RECORD_MUST_HOLD_ONE,
  55         RECORD_LOCK_ACQUIRED,
  56         RECORD_LOCK_RELEASED
  57 } RecordType;
  58
  59 void
  60 mono_locks_tracer_init (void)
  61 {
  62         char *name;
  63         InitializeCriticalSection (&tracer_lock);
  64         if (!getenv ("MONO_ENABLE_LOCK_TRACER"))
  65                 return;
  66         name = g_strdup_printf ("locks.%d", getpid ());
  67         trace_file = fopen (name, "w+");
  68         g_free (name);
  69 }
  70
  71
  72 #ifdef HAVE_EXECINFO_H
  73
  74 static int
  75 mono_backtrace (gpointer array[], int traces)
  76 {
  77         return backtrace (array, traces);
  78 }
  79
  80 #else
  81
  82 static int
  83 mono_backtrace (gpointer array[], int traces)
  84 {
  85         return 0;
  86 }
  87
  88 #endif
  89
  90 static void
  91 add_record (RecordType record_kind, RuntimeLocks kind, gpointer lock)
  92 {
  93         gpointer frames[10];
  94         char *msg;
  95         if (!trace_file)
  96                 return;
  97
  98         memset (frames, 0, sizeof (gpointer));
  99         mono_backtrace (frames, 6);
 100
 101         /*We only dump 5 frames, which should be more than enough to most analysis.*/
 102         msg = g_strdup_printf ("%x,%d,%d,%p,%p,%p,%p,%p,%p\n", (guint32)GetCurrentThreadId (), record_kind, kind, lock, frames [1], frames [2], frames [3], frames [4], frames [5]);
 103         fwrite (msg, strlen (msg), 1, trace_file);
 104         fflush (trace_file);
 105         g_free (msg);
 106 }
 107
 108 void
 109 mono_locks_lock_acquired (RuntimeLocks kind, gpointer lock)
 110 {
 111         add_record (RECORD_LOCK_ACQUIRED, kind, lock);
 112 }
 113
 114 void
 115 mono_locks_lock_released (RuntimeLocks kind, gpointer lock)
 116 {
 117         add_record (RECORD_LOCK_RELEASED, kind, lock);
 118 }
 119
 120 #endif