drd/drd_segment.c

/*
  This file is part of drd, a thread error detector.

  Copyright (C) 2006-2011 Bart Van Assche <bvanassche@acm.org>.

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; either version 2 of the
  License, or (at your option) any later version.

  This program is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  02111-1307, USA.

  The GNU General Public License is contained in the file COPYING.
*/


#include "drd_error.h"
#include "drd_segment.h"
#include "drd_thread.h"
#include "pub_tool_basics.h"      // Addr, SizeT
#include "pub_tool_libcassert.h"  // tl_assert()
#include "pub_tool_libcbase.h"    // VG_(strlen)()
#include "pub_tool_libcprint.h"   // VG_(printf)()
#include "pub_tool_machine.h"     // VG_(get_SP)()
#include "pub_tool_mallocfree.h"  // VG_(malloc)(), VG_(free)()
#include "pub_tool_threadstate.h" // VG_INVALID_THREADID


/* Local variables. */

static ULong s_segment_merge_count;
static ULong s_segments_created_count;
static ULong s_segments_alive_count;
static ULong s_max_segments_alive_count;
static Bool s_trace_segment;


/* Function definitions. */

/**
 * Initialize the memory 'sg' points at.
 *
 * @note The creator and created thread ID's may be equal.
 * @note This function copies the vector clock of thread 'creator', a technique
 *   also known as clock snooping. This will only work reliably if the thread
 *   that called pthread_create() waits until the created thread has copied
 *   the vector clock.
 */
static void sg_init(Segment* const sg,
                    const DrdThreadId creator,
                    const DrdThreadId created)
{
   Segment* creator_sg;
   ThreadId vg_created = DRD_(DrdThreadIdToVgThreadId)(created);

   tl_assert(sg);
   tl_assert(creator == DRD_INVALID_THREADID
             || DRD_(IsValidDrdThreadId)(creator));

   creator_sg = (creator != DRD_INVALID_THREADID
                 ? DRD_(thread_get_segment)(creator) : 0);

   sg->next = 0;
   sg->prev = 0;
   sg->tid = created;
   sg->refcnt = 1;

   if (vg_created != VG_INVALID_THREADID && VG_(get_SP)(vg_created) != 0)
      sg->stacktrace = VG_(record_ExeContext)(vg_created, 0);
   else
      sg->stacktrace = 0;

   if (creator_sg)
      DRD_(vc_copy)(&sg->vc, &creator_sg->vc);
   else
      DRD_(vc_init)(&sg->vc, 0, 0);
   DRD_(vc_increment)(&sg->vc, created);
   DRD_(bm_init)(&sg->bm);

   if (s_trace_segment)
   {
      char* vc;

      vc = DRD_(vc_aprint)(&sg->vc);
      VG_(message)(Vg_DebugMsg, "New segment for thread %d with vc %s\n",
                   created, vc);
      VG_(free)(vc);
   }
}

/** Deallocate the memory that was allocated by sg_init(). */
static void DRD_(sg_cleanup)(Segment* const sg)
{
   tl_assert(sg);
   tl_assert(sg->refcnt == 0);

   DRD_(vc_cleanup)(&sg->vc);
   DRD_(bm_cleanup)(&sg->bm);
}

/** Allocate and initialize a new segment. */
Segment* DRD_(sg_new)(const DrdThreadId creator, const DrdThreadId created)
{
   Segment* sg;

   s_segments_created_count++;
   s_segments_alive_count++;
   if (s_max_segments_alive_count < s_segments_alive_count)
      s_max_segments_alive_count = s_segments_alive_count;

   sg = VG_(malloc)("drd.segment.sn.1", sizeof(*sg));
   tl_assert(sg);
   sg_init(sg, creator, created);
   return sg;
}

static void DRD_(sg_delete)(Segment* const sg)
{
   if (DRD_(sg_get_trace)())
   {
      char* vc;

      vc = DRD_(vc_aprint)(&sg->vc);
      VG_(message)(Vg_DebugMsg, "Discarding the segment with vector clock %s\n",
                   vc);
      VG_(free)(vc);
   }

   s_segments_alive_count--;

   tl_assert(sg);
   DRD_(sg_cleanup)(sg);
   VG_(free)(sg);
}

/** Increment the reference count of the specified segment. */
Segment* DRD_(sg_get)(Segment* const sg)
{
   tl_assert(sg);

   sg->refcnt++;
   return sg;
}

/**
 * Decrement the reference count of the specified segment and deallocate the
 * segment if the reference count became zero.
 */
void DRD_(sg_put)(Segment* const sg)
{
   if (sg == 0)
      return;

   if (s_trace_segment)
   {
      char* vc;

      vc = DRD_(vc_aprint)(&sg->vc);
      VG_(message)(Vg_DebugMsg,
                   "Decrementing segment reference count %d -> %d with vc %s\n",
                   sg->refcnt, sg->refcnt - 1, vc);
      VG_(free)(vc);
   }

   tl_assert(sg->refcnt >= 1);

   if (--sg->refcnt == 0)
   {
      DRD_(sg_delete)(sg);
   }
}

/** Merge sg1 and sg2 into sg1. */
void DRD_(sg_merge)(Segment* const sg1, Segment* const sg2)
{
   tl_assert(sg1);
   tl_assert(sg1->refcnt == 1);
   tl_assert(sg2);
   tl_assert(sg2->refcnt == 1);

   if (s_trace_segment)
   {
      char *vc1, *vc2;

      vc1 = DRD_(vc_aprint)(&sg1->vc);
      vc2 = DRD_(vc_aprint)(&sg2->vc);

      VG_(message)(Vg_DebugMsg,
		   "Merging segments with vector clocks %s and %s\n", vc1, vc2);
      VG_(free)(vc1);
      VG_(free)(vc2);
   }

   s_segment_merge_count++;

   // Keep sg1->stacktrace.
   // Keep sg1->vc.
   // Merge sg2->bm into sg1->bm.
   DRD_(bm_merge2)(&sg1->bm, &sg2->bm);
}

/** Print the vector clock and the bitmap of the specified segment. */
void DRD_(sg_print)(Segment* const sg)
{
   tl_assert(sg);
   VG_(printf)("vc: ");
   DRD_(vc_print)(&sg->vc);
   VG_(printf)("\n");
   DRD_(bm_print)(&sg->bm);
}

/** Query whether segment tracing has been enabled. */
Bool DRD_(sg_get_trace)(void)
{
   return s_trace_segment;
}

/** Enable or disable segment tracing. */
void DRD_(sg_set_trace)(Bool const trace_segment)
{
   tl_assert(trace_segment == False || trace_segment == True);
   s_trace_segment = trace_segment;
}

ULong DRD_(sg_get_segments_created_count)(void)
{
   return s_segments_created_count;
}

ULong DRD_(sg_get_segments_alive_count)(void)
{
   return s_segments_alive_count;
}

ULong DRD_(sg_get_max_segments_alive_count)(void)
{
   return s_max_segments_alive_count;
}

ULong DRD_(sg_get_segment_merge_count)(void)
{
   return s_segment_merge_count;
}