SemaphoreManager.cc

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#ifndef PLATFORM_APERIOS

#include "SemaphoreManager.h"
#include "Shared/debuget.h"
#include "Thread.h"
#include <cstdlib>
#include <cerrno>
#include <cstdio>
#include <exception>
#include <stdexcept>
#include <iostream>
#include <sys/types.h>
#include <sys/sem.h>
#include <cstring>

#if defined(__GNU_LIBRARY__) && !defined(_SEM_SEMUN_UNDEFINED) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__MACH__)
/* union semun is defined by including <sys/sem.h> */
#else
/*! @cond INTERNAL */
/* according to X/OPEN we have to define it ourselves */
union semun {
  int val;                  /* value for SETVAL */
  struct semid_ds *buf;     /* buffer for IPC_STAT, IPC_SET */
  unsigned short *array;    /* array for GETALL, SETALL */
  /* Linux specific part: */
  struct seminfo *__buf;    /* buffer for IPC_INFO */
};
/*! @endcond */
#endif

using namespace std;

SemaphoreManager::SemaphoreManager()
: sems(), nsem(sems_t::MAX_ENTRIES), semid(-1), mysem(sems.end()), refc(sems.end())
{init();}

SemaphoreManager::SemaphoreManager(unsigned int numRequest)
: sems(), nsem(numRequest+2), semid(-1), mysem(sems.end()), refc(sems.end())
{init();}

void SemaphoreManager::init() {
  if(nsem>sems_t::MAX_ENTRIES) {
    cout << "SemaphoreManager created with request for " << nsem << " semaphores, but sems_t::MAX_ENTRIES is " << sems_t::MAX_ENTRIES << endl;
    nsem=sems_t::MAX_ENTRIES;
  }
  unsigned int req=nsem;

  //the seminfo structure is kernel-private and I can't find a portable way to access
  //SEMMSL without it.
  /*semun params; 
  seminfo info;
  params.__buf=info;
  if(semctl(semid,-1,IPC_INFO,params)<0) {
    perror("WARNING: SemaphoreManager query (semctl)");
    //we'll just forge ahead with the default value...
    //exit(EXIT_FAILURE);
  } else {
    if(nsem>info.semmsl)
      nsem=info.semmsl;
  }*/
  
  //So instead we'll do a binary search for the size:
  unsigned int lowbound=0; //inclusive
  unsigned int highbound=nsem; //inclusive
  //note that first pass asks for highbound - if it succeeds there's no search
  while(lowbound!=highbound) {
    semid=semget(IPC_PRIVATE,nsem,IPC_CREAT | IPC_EXCL | 0666);
    if(semid<0) {
      if(errno!=EINVAL && errno!=ENOSPC) {
        perror("ERROR: SemaphoreManager upper limit detection (semget)");
        exit(EXIT_FAILURE);
      }
      //too big
      highbound=nsem-1;
    } else {
      //succeeded -- too low?
      if(semctl(semid,-1,IPC_RMID)<0) {
        perror("ERROR: SemaphoreManager destruction (semctl)");
        exit(EXIT_FAILURE);
      }
      lowbound=nsem;
    }
    nsem=(lowbound+highbound+1)/2;
  }
  //get the semaphore set
  semid=semget(IPC_PRIVATE,nsem,IPC_CREAT | IPC_EXCL | 0666);
  if(semid<0) {
    perror("ERROR: SemaphoreManager construction (semget)");
        exit(EXIT_FAILURE);
  }
  if(nsem!=req)
    cerr << "WARNING: System can only allocate " << nsem << " semaphores per set for id=" << semid << " (SEMMSL or SEMMNS max reached). " << req << " were requested." << endl;
    
  //initialize to 0 (unlocked)
  unsigned short int semvals[sems_t::MAX_ENTRIES];
  for(unsigned int i=0; i<nsem; i++)
    semvals[i]=0;
  semun params; 
  params.array=semvals;
  if(semctl(semid,-1,SETALL,params)<0) {
    perror("ERROR: SemaphoreManager construction (semctl)");
    exit(EXIT_FAILURE);
  }
  
  //burn any extra ids we couldn't actually get from the system
  if(nsem!=sems_t::MAX_ENTRIES) {
    //first use up all the IDs
    while(sems.new_back()!=sems.end()) {}
    //now free the first nsem
    for(unsigned int i=0; i<nsem; i++)
      sems.pop_front();
  }
    
  //take one for ourselves to lock handing out semaphores
  mysem=sems.new_front();
  if(mysem==sems.end()) {
    cerr << "ERROR: could not allocate SemaphoreManager internal lock" << endl;
    exit(EXIT_FAILURE);
  }
  //only one semaphore can be in the process of creation or release at any given time, we have the lock
  setValue(mysem,1);
  //take another for ourselves to use as a reference count on the semaphore set
  refc=sems.new_front();
  if(refc==sems.end()) {
    cerr << "ERROR: could not allocate SemaphoreManager reference counter" << endl;
    exit(EXIT_FAILURE);
  }
  //reference count starts at 0 -- underflow is signalled by negative count
  setValue(refc,0);
  //cerr << "Semaphore set " << semid << " created" << endl;
}

SemaphoreManager::SemaphoreManager(const SemaphoreManager& mm)
: sems(), nsem(mm.nsem), semid(mm.semid), mysem(mm.mysem), refc(mm.refc)
{
  ASSERT(mm.semid!=-1,"Copy of SemaphoreManager with invalid semid!");
  lower(mysem,1); //get a lock on the new set
  sems=mm.sems; //we didn't copy sems earlier because we need a lock for this
  raise(refc,1); //add 1 to reference counter for our new set
  raise(mysem,1); //release lock on new set
  //cerr << "Semaphore set " << semid << " copied" << endl;
}

SemaphoreManager& SemaphoreManager::operator=(const SemaphoreManager& mm) {
  if(&mm==this)
    return *this;
  //ASSERT(semid!=-1,"Assignment to SemaphoreManager with invalid semid!");
  //ASSERT(mm.semid!=-1,"Assignment of SemaphoreManager with invalid semid!");
  if(semid==mm.semid) {
    //both reference the same set, just update some fields
    if(mm.semid!=-1)
      mm.lower(mm.mysem,1); //get a lock on the new set
    mysem=mm.mysem;
    sems=mm.sems;
    nsem=mm.nsem;
    if(mm.semid!=-1)
      mm.raise(mm.mysem,1); //release lock on new set
  } else {
    //we're replacing one set with the other, need to dereference our current set
    //cerr << "Semaphore set " << semid << " dereferenced" << endl;
    if(semid!=-1) {
      lower(mysem,1); //lock current set
      if(!lower(refc,1,false)) { //remove 1 from the reference counter for our current set
        //ran out of references to the old set, delete it
        //cerr << "Semaphore set " << semid << " deleted" << endl;
        sems.erase(refc);
        sems.erase(mysem);
        for(semid_t it=sems.begin(); it!=sems.end(); it=sems.next(it))
          if(it<nsem)
            cerr << "Warning: semaphore id " << it << " from set " << semid << " was still active when the set was dereferenced" << endl;
        if(semctl(semid,-1,IPC_RMID)<0) {
          perror("ERROR: SemaphoreManager deletion from operator= (semctl)");
          exit(EXIT_FAILURE);
        }
        semid=-1;
      } else
        raise(mysem,1); // it's still referenced, unlock for others
    }
    if(mm.semid!=-1)
      mm.lower(mm.mysem,1); //get a lock on the new set
    mysem=mm.mysem;
    sems=mm.sems;
    nsem=mm.nsem;
    semid=mm.semid;
    if(mm.semid!=-1) {
      raise(refc=mm.refc,1); //add 1 to reference counter for our new set
      mm.raise(mm.mysem,1); //release lock on new set
    }
    //cerr << "Semaphore set " << semid << " assigned" << endl;
  }
  return *this;
}

SemaphoreManager::~SemaphoreManager() {
  if(semid==-1)
    return;
  //cerr << "Semaphore set " << semid << " dereferenced" << endl;
  lower(mysem,1); //lock current set
  if(!lower(refc,1,false)) { //remove 1 from the reference counter for our current set
    //ran out of references to the old set, delete it
    //cerr << "Semaphore set " << semid << " deleted" << endl;
    /* // on the final shutdown, the process-local copies can't tell if semaphores were freed remotely
    sems.erase(refc);
    sems.erase(mysem);
    for(semid_t it=sems.begin(); it!=sems.end(); it=sems.next(it))
      cerr << "Warning: semaphore id " << it << " from set " << semid << " was still active when the set was dereferenced" << endl;
    */
    if(semctl(semid,-1,IPC_RMID)<0) {
      perror("ERROR: SemaphoreManager deletion from destructor (semctl)");
      exit(EXIT_FAILURE);
    }
    semid=-1;
  } else
    raise(mysem,1);
}

void SemaphoreManager::aboutToFork() {
  raise(refc,1);
}

void SemaphoreManager::faultShutdown() {
  if(semid==-1)
    return; // already released set
  if(semctl(semid,-1,IPC_RMID)<0)
    perror("WARNING: SemaphoreManager faultShutdown (semctl)");
  semid=-1;
}

SemaphoreManager::semid_t SemaphoreManager::getSemaphore() {
  lower(mysem,1);
  semid_t id=sems.new_front();
  raise(mysem,1);
  if(id!=sems.end())
    setValue(id,0);
  intrPolicy[id]=INTR_RETRY;
  return id;
}
void SemaphoreManager::releaseSemaphore(semid_t id) {
  lower(mysem,1);
  sems.erase(id);
  raise(mysem,1);
}

bool SemaphoreManager::lower(semid_t id, unsigned int x, bool block/*=true*/) const {
  sembuf sb={id,-x,(block?0:IPC_NOWAIT)};
  while(true) {
    Thread::requestInterruptOnCancel();
    int res = semop(semid,&sb,1);
    int theErr = errno;
    Thread::unrequestInterruptOnCancel();
    if(res==0)
      break;
    if(theErr==EAGAIN)
      return false;
    if(theErr==EINTR) {
      switch(intrPolicy[id]) {
        case INTR_CANCEL_VERBOSE:
          perror("ERROR: SemaphoreManager unable to lower semaphore (semop)");
          cerr << "       semop was interrupted by signal, cancelling lower()";
        case INTR_CANCEL:
          return false;
        case INTR_RETRY_VERBOSE:
          perror("ERROR: SemaphoreManager unable to lower semaphore (semop)");
          cerr << "       semop was interrupted by signal.  Trying again...";
          break;
        case INTR_RETRY:
          break; //while loop will retry
        case INTR_THROW_VERBOSE:
          perror("ERROR: SemaphoreManager unable to lower semaphore (semop)");
          cerr << "       semop was interrupted by signal.  Throwing exception...";
        case INTR_THROW:
          throw std::runtime_error("EINTR returned by lower semop");
        case INTR_EXIT:
          perror("ERROR: SemaphoreManager unable to lower semaphore (semop)");
          cerr << "       semop was interrupted by signal.  Exiting...";
          exit(EXIT_FAILURE);
      }
    } else {
      if(theErr==EIDRM)
        usleep(500000); // probably in the process of shutdown, wait half a second before complaining
      cerr << "ERROR: SemaphoreManager unable to lower semaphore (semop): " << strerror(theErr) << endl;
      cerr << "       ";
      if(theErr==EIDRM) {
        cerr << "Semaphore set has been removed.  " << endl;
      }
      if(theErr==EINVAL) {
        cerr << "Semaphore set was deleted.  " << endl;
      }
      //prevent recuring problems
      cerr << "Goodbye" << endl;
      exit(EXIT_FAILURE);
    }
  }
  return true;
}
void SemaphoreManager::raise(semid_t id, unsigned int x) const {
  sembuf sb={id,x,0};
  if(semop(semid,&sb,1)<0) {
    perror("ERROR: SemaphoreManager unable to raise semaphore (semop)");
  }
}
int SemaphoreManager::getValue(semid_t id) const {
  int ans=semctl(semid,id,GETVAL);
  if(ans<0)
    perror("ERROR: SemaphoreManager getValue (semctl)");
  return ans;
}
void SemaphoreManager::setValue(semid_t id, int x) const {
  semun params; 
  params.val=x;
  if(semctl(semid,id,SETVAL,params)<0) {
    perror("ERROR: SemaphoreManager::setValue (semctl)");
    exit(EXIT_FAILURE);
  }
}
int SemaphoreManager::getNumZeroBlockers(semid_t id) const {
  int ans=semctl(semid,id,GETZCNT);
  if(ans<0)
    perror("ERROR: SemaphoreManager getNumZeroBlockers (semctl)");
  return ans;
}
bool SemaphoreManager::testZero(semid_t id, bool block/*=true*/) const {
  sembuf sb={id,0,(block?0:IPC_NOWAIT)};
  while(true) {
    Thread::requestInterruptOnCancel();
    int res = semop(semid,&sb,1);
    int theErr = errno;
    Thread::unrequestInterruptOnCancel();
    if(res==0)
      break;
    if(theErr==EAGAIN)
      return false;
    if(theErr!=EINTR) { // && theErr!=ERESTART?
      if(theErr==EIDRM)
        usleep(500000); // probably in the process of shutdown, wait half a second before complaining
      cerr << "ERROR: SemaphoreManager unable to testZero() (semop): " << strerror(theErr) << '\n';
      cerr << "       ";
      if(theErr==EIDRM) {
        cerr << "Semaphore set has been removed.  " << endl;
      } else if(theErr==EINVAL) {
        cerr << "Semaphore set was deleted.  " << endl;
      } else {
        cerr << "Error code was " << theErr << endl;
      }
      cerr << "Goodbye" << endl;
      exit(EXIT_FAILURE);
    } else {
      switch(intrPolicy[id]) {
        case INTR_CANCEL_VERBOSE:
          perror("ERROR: SemaphoreManager unable to testZero (semop)");
          cerr << "       semop was interrupted by signal, cancelling testZero()";
        case INTR_CANCEL:
          return false;
        case INTR_RETRY_VERBOSE:
          perror("ERROR: SemaphoreManager unable to testZero (semop)");
          cerr << "       semop was interrupted by signal.  Trying again...";
          break;
        case INTR_RETRY:
          break; //while loop will retry
        case INTR_THROW_VERBOSE:
          perror("ERROR: SemaphoreManager unable to testZero (semop)");
          cerr << "       semop was interrupted by signal.  Throwing exception...";
        case INTR_THROW:
          throw std::runtime_error("EINTR returned by testZero semop");
        case INTR_EXIT:
          perror("ERROR: SemaphoreManager unable to testZero (semop)");
          cerr << "       semop was interrupted by signal.  Exiting...";
          exit(EXIT_FAILURE);
      }
    }
  }
  return true;
}
bool SemaphoreManager::testZero_add(semid_t id, int x, bool testblock/*=true*/, bool addblock/*=true*/) const {
  sembuf sb[2]={
    {id,0,(testblock?0:IPC_NOWAIT)},
    {id,x,(addblock?0:IPC_NOWAIT)}
  };
  while(true) {
    Thread::requestInterruptOnCancel();
    int res = semop(semid,sb,2);
    int theErr = errno;
    try {
      Thread::unrequestInterruptOnCancel();
    } catch(...) { // thread cancelled
      if(res==0) { // if we weren't interrupted, then semop was successful, undo it
#ifdef DEBUG
        ASSERT(lower(id,x,false),"Could not undo semop after thread cancel in testZero_add (would block?)");
#else
        lower(id,x,true); // block should not occur
#endif
      }
      throw;
    }
    if(res==0)
      break;
    if(theErr==EAGAIN)
      return false;
    if(theErr!=EINTR) { // && theErr!=ERESTART?
      if(theErr==EIDRM)
        usleep(500000); // probably in the process of shutdown, wait half a second before complaining
      cerr << "ERROR: SemaphoreManager unable to testZero_add() (semop): " << strerror(theErr) << '\n';
      cerr << "       ";
      if(theErr==EIDRM) {
        cerr << "Semaphore set has been removed.  " << endl;
      } else if(theErr==EINVAL) {
        cerr << "Semaphore set was deleted.  " << endl;
      } else {
        cerr << "Error code was " << theErr << endl;
      }
      cerr << "Goodbye" << endl;
      exit(EXIT_FAILURE);
    } else {
      switch(intrPolicy[id]) {
        case INTR_CANCEL_VERBOSE:
          perror("ERROR: SemaphoreManager unable to testZero_add (semop)");
          cerr << "       semop was interrupted by signal, cancelling testZero_add()";
        case INTR_CANCEL:
          return false;
        case INTR_RETRY_VERBOSE:
          perror("ERROR: SemaphoreManager unable to testZero_add (semop)");
          cerr << "       semop was interrupted by signal.  Trying again...";
          break;
        case INTR_RETRY:
          break; //while loop will retry
        case INTR_THROW_VERBOSE:
          perror("ERROR: SemaphoreManager unable to testZero_add (semop)");
          cerr << "       semop was interrupted by signal.  Throwing exception...";
        case INTR_THROW:
          throw std::runtime_error("EINTR returned by testZero_add semop");
        case INTR_EXIT:
          perror("ERROR: SemaphoreManager unable to testZero_add (semop)");
          cerr << "       semop was interrupted by signal.  Exiting...";
          exit(EXIT_FAILURE);
      }
    }
  }
  return true;
}
bool SemaphoreManager::add_testZero(semid_t id, int x, bool addblock/*=true*/, bool testblock/*=true*/) const {
  sembuf sb[2]={
    {id,x,(addblock?0:IPC_NOWAIT)},
    {id,0,(testblock?0:IPC_NOWAIT)}
  };
  while(true) {
    Thread::requestInterruptOnCancel();
    int res = semop(semid,sb,2);
    int theErr = errno;
    Thread::unrequestInterruptOnCancel();
    if(res==0)
      break;
    if(theErr==EAGAIN)
      return false;
    if(theErr!=EINTR) { // && theErr!=ERESTART?
      if(theErr==EIDRM)
        usleep(500000); // probably in the process of shutdown, wait half a second before complaining
      cerr << "ERROR: SemaphoreManager unable to add_testZero() (semop): " << strerror(theErr) << '\n';
      cerr << "       ";
      if(theErr==EIDRM) {
        cerr << "Semaphore set has been removed.  " << endl;
      } else if(theErr==EINVAL) {
        cerr << "Semaphore set was deleted.  " << endl;
      } else {
        cerr << "Error code was " << theErr << endl;
      }
      cerr << "Goodbye" << endl;
      exit(EXIT_FAILURE);
    } else {
      switch(intrPolicy[id]) {
        case INTR_CANCEL_VERBOSE:
          perror("ERROR: SemaphoreManager unable to add_testZero (semop)");
          cerr << "       semop was interrupted by signal, cancelling add_testZero()";
        case INTR_CANCEL:
          return false;
        case INTR_RETRY_VERBOSE:
          perror("ERROR: SemaphoreManager unable to add_testZero (semop)");
          cerr << "       semop was interrupted by signal.  Trying again...";
          break;
        case INTR_RETRY:
          break; //while loop will retry
        case INTR_THROW_VERBOSE:
          perror("ERROR: SemaphoreManager unable to add_testZero (semop)");
          cerr << "       semop was interrupted by signal.  Throwing exception...";
        case INTR_THROW:
          throw std::runtime_error("EINTR returned by add_testZero semop");
        case INTR_EXIT:
          perror("ERROR: SemaphoreManager unable to add_testZero (semop)");
          cerr << "       semop was interrupted by signal.  Exiting...";
          exit(EXIT_FAILURE);
      }
    }
  }
  return true;
}

bool SemaphoreManager::add_testZero_add(semid_t id, int x1, int x2, bool add1block/*=true*/, bool testblock/*=true*/, bool add2block/*=true*/) const {
  sembuf sb[3]={
    {id,x1,(add1block?0:IPC_NOWAIT)},
    {id,0,(testblock?0:IPC_NOWAIT)},
    {id,x2,(add2block?0:IPC_NOWAIT)}
  };
  while(true) {
    Thread::requestInterruptOnCancel();
    int res = semop(semid,sb,3);
    int theErr = errno;
    Thread::unrequestInterruptOnCancel();
    if(res==0)
      break;
    if(theErr==EAGAIN)
      return false;
    if(theErr!=EINTR) { // && theErr!=ERESTART?
      if(theErr==EIDRM)
        usleep(500000); // probably in the process of shutdown, wait half a second before complaining
      cerr << "ERROR: SemaphoreManager unable to add_testZero() (semop): " << strerror(theErr) << '\n';
      cerr << "       ";
      if(theErr==EIDRM) {
        cerr << "Semaphore set has been removed.  " << endl;
      } else if(theErr==EINVAL) {
        cerr << "Semaphore set was deleted.  " << endl;
      } else {
        cerr << "Error code was " << theErr << endl;
      }
      cerr << "Goodbye" << endl;
      exit(EXIT_FAILURE);
    } else {
      switch(intrPolicy[id]) {
        case INTR_CANCEL_VERBOSE:
          perror("ERROR: SemaphoreManager unable to add_testZero (semop)");
          cerr << "       semop was interrupted by signal, cancelling add_testZero()";
        case INTR_CANCEL:
          return false;
        case INTR_RETRY_VERBOSE:
          perror("ERROR: SemaphoreManager unable to add_testZero (semop)");
          cerr << "       semop was interrupted by signal.  Trying again...";
          break;
        case INTR_RETRY:
          break; //while loop will retry
        case INTR_THROW_VERBOSE:
          perror("ERROR: SemaphoreManager unable to add_testZero (semop)");
          cerr << "       semop was interrupted by signal.  Throwing exception...";
        case INTR_THROW:
          throw std::runtime_error("EINTR returned by add_testZero semop");
        case INTR_EXIT:
          perror("ERROR: SemaphoreManager unable to add_testZero (semop)");
          cerr << "       semop was interrupted by signal.  Exiting...";
          exit(EXIT_FAILURE);
      }
    }
  }
  return true;
}

/*! @file
 * @brief Implements SemaphoreManager, which initializes, manages, and releases a set of System V style semaphores
 * @author ejt (Creator)
 */

#endif //Aperios check