drd/drd_barrier.c

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

  Copyright (C) 2006-2009 Bart Van Assche <bart.vanassche@gmail.com>.

  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_barrier.h"
#include "drd_clientobj.h"
#include "drd_error.h"
#include "drd_suppression.h"
#include "pub_tool_errormgr.h"    // VG_(maybe_record_error)()
#include "pub_tool_libcassert.h"  // tl_assert()
#include "pub_tool_libcprint.h"   // VG_(printf)()
#include "pub_tool_machine.h"     // VG_(get_IP)()
#include "pub_tool_mallocfree.h"  // VG_(malloc)(), VG_(free)()
#include "pub_tool_oset.h"
#include "pub_tool_threadstate.h" // VG_(get_running_tid)()


/* Type definitions. */

/** Information associated with one thread participating in a barrier. */
struct barrier_thread_info
{
  UWord       tid;           // A DrdThreadId declared as UWord because
                             // this member variable is the key of an OSet.
  Word        iteration;     // iteration of last pthread_barrier_wait()
                             // call thread tid participated in.
  Segment*    sg[2];         // Segments of the last two
                             // pthread_barrier() calls by thread tid.
  ExeContext* wait_call_ctxt;// call stack for *_barrier_wait() call.
  Segment*    post_wait_sg;  // Segment created after *_barrier_wait() finished
};


/* Local functions. */

static void barrier_cleanup(struct barrier_info* p);
static void barrier_delete_thread(struct barrier_info* const p,
                                  const DrdThreadId tid);
static const char* barrier_get_typename(struct barrier_info* const p);
static const char* barrier_type_name(const BarrierT bt);
static
void barrier_report_wait_delete_race(const struct barrier_info* const p,
                                    const struct barrier_thread_info* const q);


/* Local variables. */

static Bool  s_trace_barrier = False;
static ULong s_barrier_segment_creation_count;


/* Function definitions. */

void DRD_(barrier_set_trace)(const Bool trace_barrier)
{
  s_trace_barrier = trace_barrier;
}

/**
 * Initialize the structure *p with the specified thread ID and iteration
 * information.
 */
static
void DRD_(barrier_thread_initialize)(struct barrier_thread_info* const p,
                                     const DrdThreadId tid,
                                     const Word iteration)
{
  p->tid            = tid;
  p->iteration      = iteration;
  p->sg[0]          = 0;
  p->sg[1]          = 0;
  p->wait_call_ctxt = 0;
  p->post_wait_sg   = 0;
}

/**
 * Deallocate the memory that is owned by members of
 * struct barrier_thread_info.
 */
static void DRD_(barrier_thread_destroy)(struct barrier_thread_info* const p)
{
  tl_assert(p);
  DRD_(sg_put)(p->sg[0]);
  DRD_(sg_put)(p->sg[1]);
  DRD_(sg_put)(p->post_wait_sg);
}

/**
 * Initialize the structure *p with the specified client-side barrier address,
 * barrier object size and number of participants in each barrier.
 */
static
void DRD_(barrier_initialize)(struct barrier_info* const p,
                              const Addr barrier,
                              const BarrierT barrier_type,
                              const Word count)
{
  tl_assert(barrier != 0);
  tl_assert(barrier_type == pthread_barrier || barrier_type == gomp_barrier);
  tl_assert(p->a1 == barrier);

  p->cleanup           = (void(*)(DrdClientobj*))barrier_cleanup;
  p->delete_thread
    = (void(*)(DrdClientobj*, DrdThreadId))barrier_delete_thread;
  p->barrier_type      = barrier_type;
  p->count             = count;
  p->pre_iteration     = 0;
  p->post_iteration    = 0;
  p->pre_waiters_left  = count;
  p->post_waiters_left = count;

  tl_assert(sizeof(((struct barrier_thread_info*)0)->tid) == sizeof(Word));
  tl_assert(sizeof(((struct barrier_thread_info*)0)->tid)
            >= sizeof(DrdThreadId));
  p->oset = VG_(OSetGen_Create)(0, 0, VG_(malloc), "drd.barrier.bi.1",
                                      VG_(free));
}

/**
 * Deallocate the memory owned by the struct barrier_info object and also
 * all the nodes in the OSet p->oset.
 *
 * Called by clientobj_destroy().
 */
static void barrier_cleanup(struct barrier_info* p)
{
  struct barrier_thread_info* q;
    Segment* latest_sg = 0;

  tl_assert(p);

  if (p->pre_waiters_left != p->count)
  {
    BarrierErrInfo bei = { p->a1, 0, 0 };
    VG_(maybe_record_error)(VG_(get_running_tid)(),
                            BarrierErr,
                            VG_(get_IP)(VG_(get_running_tid)()),
                            "Destruction of barrier that is being waited"
                            " upon",
                            &bei);
  }

  DRD_(thread_get_latest_segment)(&latest_sg, DRD_(thread_get_running_tid)());
  tl_assert(latest_sg);

  VG_(OSetGen_ResetIter)(p->oset);
  for ( ; (q = VG_(OSetGen_Next)(p->oset)) != 0; )
  {
    if (q->post_wait_sg
        && ! DRD_(vc_lte)(&q->post_wait_sg->vc, &latest_sg->vc))
    {
      barrier_report_wait_delete_race(p, q);
    }

    DRD_(barrier_thread_destroy)(q);
  }
  VG_(OSetGen_Destroy)(p->oset);

  DRD_(sg_put)(latest_sg);
}

/**
 * Look up the client-side barrier address barrier in s_barrier[]. If not
 * found, add it.
 */
static
struct barrier_info*
DRD_(barrier_get_or_allocate)(const Addr barrier,
                              const BarrierT barrier_type, const Word count)
{
  struct barrier_info *p;

  tl_assert(barrier_type == pthread_barrier || barrier_type == gomp_barrier);

  tl_assert(offsetof(DrdClientobj, barrier) == 0);
  p = &(DRD_(clientobj_get)(barrier, ClientBarrier)->barrier);
  if (p == 0)
  {
    p = &(DRD_(clientobj_add)(barrier, ClientBarrier)->barrier);
    DRD_(barrier_initialize)(p, barrier, barrier_type, count);
  }
  return p;
}

/**
 * Look up the address of the information associated with the client-side
 * barrier object.
 */
static struct barrier_info* DRD_(barrier_get)(const Addr barrier)
{
  tl_assert(offsetof(DrdClientobj, barrier) == 0);
  return &(DRD_(clientobj_get)(barrier, ClientBarrier)->barrier);
}

/**
 * Initialize a barrier with client address barrier, client size size, and
 * where count threads participate in each barrier.
 *
 * Called before pthread_barrier_init().
 */
void DRD_(barrier_init)(const Addr barrier,
                        const BarrierT barrier_type, const Word count,
                        const Bool reinitialization)
{
  struct barrier_info* p;

  tl_assert(barrier_type == pthread_barrier || barrier_type == gomp_barrier);

  if (count == 0)
  {
    BarrierErrInfo bei = { barrier, 0, 0 };
    VG_(maybe_record_error)(VG_(get_running_tid)(),
                            BarrierErr,
                            VG_(get_IP)(VG_(get_running_tid)()),
                            "pthread_barrier_init: 'count' argument is zero",
                            &bei);
  }

  if (! reinitialization && barrier_type == pthread_barrier)
  {
    p = DRD_(barrier_get)(barrier);
    if (p)
    {
      BarrierErrInfo bei = { barrier, 0, 0 };
      VG_(maybe_record_error)(VG_(get_running_tid)(),
                              BarrierErr,
                              VG_(get_IP)(VG_(get_running_tid)()),
                              "Barrier reinitialization",
                              &bei);
    }
  }
  p = DRD_(barrier_get_or_allocate)(barrier, barrier_type, count);

  if (s_trace_barrier)
  {
    if (reinitialization)
    {
      VG_(message)(Vg_UserMsg,
                   "[%d/%d] barrier_reinit    %s 0x%lx count %ld -> %ld",
                   VG_(get_running_tid)(),
                   DRD_(thread_get_running_tid)(),
                   barrier_get_typename(p),
                   barrier,
                   p->count,
                   count);
    }
    else
    {
      VG_(message)(Vg_UserMsg,
                   "[%d/%d] barrier_init      %s 0x%lx",
                   VG_(get_running_tid)(),
                   DRD_(thread_get_running_tid)(),
                   barrier_get_typename(p),
                   barrier);
    }
  }

  if (reinitialization && p->count != count)
  {
    if (p->pre_waiters_left != p->count || p->post_waiters_left != p->count)
    {
      BarrierErrInfo bei = { p->a1, 0, 0 };
      VG_(maybe_record_error)(VG_(get_running_tid)(),
                              BarrierErr,
                              VG_(get_IP)(VG_(get_running_tid)()),
                              "Reinitialization of barrier with active"
                              " waiters",
                              &bei);
    }
    p->count = count;
  }
}

/** Called after pthread_barrier_destroy() / gomp_barrier_destroy(). */
void DRD_(barrier_destroy)(const Addr barrier, const BarrierT barrier_type)
{
  struct barrier_info* p;

  p = DRD_(barrier_get)(barrier);

  if (s_trace_barrier)
  {
    VG_(message)(Vg_UserMsg,
                 "[%d/%d] barrier_destroy   %s 0x%lx",
                 VG_(get_running_tid)(),
                 DRD_(thread_get_running_tid)(),
                 barrier_get_typename(p),
                 barrier);
  }

  if (p == 0)
  {
    GenericErrInfo GEI;
    VG_(maybe_record_error)(VG_(get_running_tid)(),
                            GenericErr,
                            VG_(get_IP)(VG_(get_running_tid)()),
                            "Not a barrier",
                            &GEI);
    return;
  }

  if (p->pre_waiters_left != p->count || p->post_waiters_left != p->count)
  {
    BarrierErrInfo bei = { p->a1, 0, 0 };
    VG_(maybe_record_error)(VG_(get_running_tid)(),
                            BarrierErr,
                            VG_(get_IP)(VG_(get_running_tid)()),
                            "Destruction of a barrier with active waiters",
                            &bei);
  }

  DRD_(clientobj_remove)(p->a1, ClientBarrier);
}

/** Called before pthread_barrier_wait() / gomp_barrier_wait(). */
void DRD_(barrier_pre_wait)(const DrdThreadId tid, const Addr barrier,
                            const BarrierT barrier_type)
{
  struct barrier_info* p;
  struct barrier_thread_info* q;
  const UWord word_tid = tid;

  p = DRD_(barrier_get)(barrier);
  if (p == 0 && barrier_type == gomp_barrier)
  {
    /*
     * gomp_barrier_wait() call has been intercepted but gomp_barrier_init()
     * not. The only cause I know of that can trigger this is that libgomp.so
     * has been compiled with --enable-linux-futex.
     */
    VG_(message)(Vg_UserMsg, "");
    VG_(message)(Vg_UserMsg,
                 "Please verify whether gcc has been configured"
                 " with option --disable-linux-futex.");
    VG_(message)(Vg_UserMsg,
                 "See also the section about OpenMP in the DRD manual.");
    VG_(message)(Vg_UserMsg, "");
  }
  tl_assert(p);

  if (s_trace_barrier)
  {
    VG_(message)(Vg_UserMsg,
                 "[%d/%d] barrier_pre_wait  %s 0x%lx iteration %ld",
                 VG_(get_running_tid)(),
                 DRD_(thread_get_running_tid)(),
                 barrier_get_typename(p),
                 barrier,
                 p->pre_iteration);
  }

  /* Allocate the per-thread data structure if necessary. */
  q = VG_(OSetGen_Lookup)(p->oset, &word_tid);
  if (q == 0)
  {
    q = VG_(OSetGen_AllocNode)(p->oset, sizeof(*q));
    DRD_(barrier_thread_initialize)(q, tid, p->pre_iteration);
    VG_(OSetGen_Insert)(p->oset, q);
    tl_assert(VG_(OSetGen_Lookup)(p->oset, &word_tid) == q);
  }

  /* Record *_barrier_wait() call context. */
  q->wait_call_ctxt = VG_(record_ExeContext)(VG_(get_running_tid)(), 0);

  /*
   * Store a pointer to the latest segment of the current thread in the
   * per-thread data structure.
   */
  DRD_(thread_get_latest_segment)(&q->sg[p->pre_iteration], tid);

  /*
   * If the same number of threads as the barrier count indicates have
   * called the pre *_barrier_wait() wrapper, toggle p->pre_iteration and
   * reset the p->pre_waiters_left counter.
   */
  if (--p->pre_waiters_left <= 0)
  {
    p->pre_iteration    = 1 - p->pre_iteration;
    p->pre_waiters_left = p->count;
  }
}

/** Called after pthread_barrier_wait() / gomp_barrier_wait(). */
void DRD_(barrier_post_wait)(const DrdThreadId tid, const Addr barrier,
                             const BarrierT barrier_type, const Bool waited,
                             const Bool serializing)
{
  struct barrier_info* p;
  const UWord word_tid = tid;
  struct barrier_thread_info* q;
  struct barrier_thread_info* r;

  p = DRD_(barrier_get)(barrier);

  if (s_trace_barrier)
  {
    VG_(message)(Vg_UserMsg,
                 "[%d/%d] barrier_post_wait %s 0x%lx iteration %ld%s",
                 VG_(get_running_tid)(),
                 tid,
                 p ? barrier_get_typename(p) : "(?)",
                 barrier,
                 p ? p->post_iteration : -1,
                 serializing ? " (serializing)" : "");
  }

  /*
   * If p == 0, this means that the barrier has been destroyed after
   * *_barrier_wait() returned and before this function was called. Just
   * return in that case -- race conditions between *_barrier_wait()
   * and *_barrier_destroy() are detected by the *_barrier_destroy() wrapper.
   */
  if (p == 0)
    return;

  /* If the *_barrier_wait() call returned an error code, exit. */
  if (! waited)
    return;

  q = VG_(OSetGen_Lookup)(p->oset, &word_tid);
  if (q == 0)
  {
    BarrierErrInfo bei = { p->a1, 0, 0 };
    VG_(maybe_record_error)(VG_(get_running_tid)(),
                            BarrierErr,
                            VG_(get_IP)(VG_(get_running_tid)()),
                            "Error in barrier implementation"
                            " -- barrier_wait() started before"
                            " barrier_destroy() and finished after"
                            " barrier_destroy()",
                            &bei);

    q = VG_(OSetGen_AllocNode)(p->oset, sizeof(*q));
    DRD_(barrier_thread_initialize)(q, tid, p->pre_iteration);
    VG_(OSetGen_Insert)(p->oset, q);
    tl_assert(VG_(OSetGen_Lookup)(p->oset, &word_tid) == q);
  }
  /*
   * Combine all vector clocks that were stored in the pre_barrier_wait
   * wrapper with the vector clock of the current thread.
   */
  VG_(OSetGen_ResetIter)(p->oset);
  for ( ; (r = VG_(OSetGen_Next)(p->oset)) != 0; )
  {
    if (r != q)
    {
      tl_assert(r->sg[p->post_iteration]);
      DRD_(thread_combine_vc2)(tid, &r->sg[p->post_iteration]->vc);
    }
  }

  /* Create a new segment and store a pointer to that segment. */
  DRD_(thread_new_segment)(tid);
  DRD_(thread_get_latest_segment)(&q->post_wait_sg, tid);
  s_barrier_segment_creation_count++;

  /*
   * If the same number of threads as the barrier count indicates have
   * called the post *_barrier_wait() wrapper, toggle p->post_iteration and
   * reset the p->post_waiters_left counter.
   */
  if (--p->post_waiters_left <= 0)
  {
    p->post_iteration    = 1 - p->post_iteration;
    p->post_waiters_left = p->count;
  }
}

/** Called when thread tid stops to exist. */
static void barrier_delete_thread(struct barrier_info* const p,
                                  const DrdThreadId tid)
{
  struct barrier_thread_info* q;
  const UWord word_tid = tid;

  q = VG_(OSetGen_Remove)(p->oset, &word_tid);

  /*
   * q is only non-zero if the barrier object has been used by thread tid
   * after the barrier_init() call and before the thread finished.
   */
  if (q)
  {
    DRD_(barrier_thread_destroy)(q);
    VG_(OSetGen_FreeNode)(p->oset, q);
  }
}

/**
 * Report that *_barrier_destroy() has been called but that this call was
 * not synchronized with the last *_barrier_wait() call on the same barrier.
 *
 * This topic has been discussed extensively on comp.programming.threads
 * (February 3, 2009). See also
 * <a href="http://groups.google.com/group/comp.programming.threads/browse_thread/thread/4f65535d6192aa50/a5f4bf1e3b437c4d">Immediately destroying pthread barriers</a>.
 */
static
void barrier_report_wait_delete_race(const struct barrier_info* const p,
                                     const struct barrier_thread_info* const q)
{
  tl_assert(p);
  tl_assert(q);

  {
    BarrierErrInfo bei
      = { p->a1, q->tid, q->wait_call_ctxt };
    VG_(maybe_record_error)(VG_(get_running_tid)(),
                            BarrierErr,
                            VG_(get_IP)(VG_(get_running_tid)()),
                            "Destruction of barrier not synchronized with"
                            " barrier wait call",
                            &bei);
  }
}

static const char* barrier_get_typename(struct barrier_info* const p)
{
  tl_assert(p);

  return barrier_type_name(p->barrier_type);
}

static const char* barrier_type_name(const BarrierT bt)
{
  switch (bt)
  {
  case pthread_barrier:
    return "pthread barrier";
  case gomp_barrier:
    return "gomp barrier";
  }
  return "?";
}

ULong DRD_(get_barrier_segment_creation_count)(void)
{
  return s_barrier_segment_creation_count;
}