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// SV_Semaphore_Complex.cpp
// $Id$
#include "ace/SV_Semaphore_Complex.h"
#include "ace/Log_Msg.h"
#include "ace/OS_NS_Thread.h"
#if !defined (__ACE_INLINE__)
#include "ace/SV_Semaphore_Complex.i"
#endif /* __ACE_INLINE__ */
ACE_RCSID(ace, SV_Semaphore_Complex, "$Id$")
ACE_ALLOC_HOOK_DEFINE(ACE_SV_Semaphore_Complex)
void
ACE_SV_Semaphore_Complex::dump (void) const
{
#if defined (ACE_HAS_DUMP)
ACE_TRACE ("ACE_SV_Semaphore_Complex::dump");
#endif /* ACE_HAS_DUMP */
}
// initial value of process
const int ACE_SV_Semaphore_Complex::BIGCOUNT_ = 10000;
// Define the ACE_SV_Semaphore operation arrays for the semop() calls.
sembuf ACE_SV_Semaphore_Complex::op_lock_[2] =
{
{0, 0, 0}, // Wait for [0] (lock) to equal 0
{0, 1, SEM_UNDO}, // then increment [0] to 1 - this locks it.
// UNDO to release the lock if processes exit
// before explicitly unlocking.
};
sembuf ACE_SV_Semaphore_Complex::op_endcreate_[2] =
{
{1, -1, SEM_UNDO}, // Decrement [1] (proc counter) with undo on
// exit, UNDO to adjust proc counter if
// process exits before explicitly calling close()
{0, -1, SEM_UNDO}, // the decrement [0] (lock) back to 0
};
sembuf ACE_SV_Semaphore_Complex::op_open_[1] =
{
{1, -1, SEM_UNDO}, // Decrement [1] (proc counter) with undo on
// exit.
};
sembuf ACE_SV_Semaphore_Complex::op_close_[3] =
{
{0, 0, 0}, // Wait for [0] (lock) to equal 0
{0, 1, SEM_UNDO}, // then increment [0] to 1 - this lock it
{1, 1, SEM_UNDO}, // then increment [1] (proc counter)
};
sembuf ACE_SV_Semaphore_Complex::op_unlock_[1] =
{
{0, -1, SEM_UNDO}, // Decrement [0] (lock) back to 0
};
// Open or create an array of SV_Semaphores. We return 0 if all is OK, else -1.
int
ACE_SV_Semaphore_Complex::open (key_t k,
int create,
int initial_value,
u_short nsems,
int perms)
{
ACE_TRACE ("ACE_SV_Semaphore_Complex::open");
if (k == IPC_PRIVATE)
return -1;
this->key_ = k;
// Must include a count for the 2 additional semaphores we use
// internally.
this->sem_number_ = nsems + 2;
if (create == ACE_SV_Semaphore_Complex::ACE_CREATE)
{
int result;
do
{
this->internal_id_ = ACE_OS::semget
(this->key_,
(u_short) 2 + nsems,
perms | ACE_SV_Semaphore_Complex::ACE_CREATE);
if (this->internal_id_ == -1)
return -1; // permission problem or tables full
// When the <ACE_SV_Semaphore_Complex> is created, we know
// that the value of all 3 members is 0. Get a lock on the
// <ACE_SV_Semaphore_Complex> by waiting for [0] to equal 0,
// then increment it.
// There is a race condition here. There is the possibility
// that between the <semget> above and the <semop> below,
// another process can call out <close> function which can
// remove the <ACE_SV_Semaphore> if that process is the last
// one using it. Therefor we handle the error condition of
// an invalid <ACE_SV_Semaphore> ID specifically below, and
// if it does happen, we just go back and create it again.
result = ACE_OS::semop (this->internal_id_,
&ACE_SV_Semaphore_Complex::op_lock_[0],
2);
}
while (result == -1 && (errno == EINVAL || errno == EIDRM));
if (result == -1)
return -1;
// Get the value of the process counter. If it equals 0, then no
// one has initialized the ACE_SV_Semaphore yet.
int semval = ACE_SV_Semaphore_Simple::control (GETVAL, 0, 1);
if (semval == -1)
return this->init ();
else if (semval == 0)
{
// We should initialize by doing a SETALL, but that would
// clear the adjust value that we set when we locked the
// ACE_SV_Semaphore above. Instead we do system calls to
// initialize [1], as well as all the nsems SV_Semaphores.
if (ACE_SV_Semaphore_Simple::control (SETVAL,
ACE_SV_Semaphore_Complex::BIGCOUNT_,
1) == -1)
return -1;
else
for (int i = 0; i < nsems; i++)
if (this->control (SETVAL, initial_value, i) == -1)
return -1;
}
// Decrement the process counter and then release the lock.
return ACE_OS::semop (this->internal_id_,
&ACE_SV_Semaphore_Complex::op_endcreate_[0],
2);
}
else
{
this->internal_id_ = ACE_OS::semget (this->key_, 2 + nsems, 0);
if (this->internal_id_ == -1)
return -1; // doesn't exist or tables full
// Decrement the process counter. We don't need a lock to do this.
if (ACE_OS::semop (this->internal_id_,
&ACE_SV_Semaphore_Complex::op_open_[0], 1) < 0)
return this->init ();
return 0;
}
}
int
ACE_SV_Semaphore_Complex::open (const char *name,
int flags,
int initial_value,
u_short nsems,
int perms)
{
ACE_TRACE ("ACE_SV_Semaphore_Complex::open");
return this->open (ACE_SV_Semaphore_Simple::name_2_key (name),
flags, initial_value, nsems, perms);
}
// Close a ACE_SV_Semaphore. Unlike the remove above, this function
// is for a process to call before it exits, when it is done with the
// ACE_SV_Semaphore. We "decrement" the counter of processes using
// the ACE_SV_Semaphore, and if this was the last one, we can remove
// the ACE_SV_Semaphore.
int
ACE_SV_Semaphore_Complex::close (void)
{
ACE_TRACE ("ACE_SV_Semaphore_Complex::close");
int semval;
if (this->key_ == (key_t) - 1 || this->internal_id_ == -1)
return -1;
// The following semop() first gets a lock on the ACE_SV_Semaphore,
// then increments [1] - the process number.
if (ACE_OS::semop (this->internal_id_,
&ACE_SV_Semaphore_Complex::op_close_[0],
3) == -1)
return -1;
// Now that we have a lock, read the value of the process counter to
// see if this is the last reference to the ACE_SV_Semaphore. There
// is a race condition here - see the comments in create ().
if ((semval = ACE_SV_Semaphore_Simple::control (GETVAL, 0, 1)) == -1)
return -1;
if (semval > ACE_SV_Semaphore_Complex::BIGCOUNT_)
return -1;
else if (semval == ACE_SV_Semaphore_Complex::BIGCOUNT_)
return this->remove ();
else
{
int result = ACE_OS::semop (this->internal_id_,
&ACE_SV_Semaphore_Complex::op_unlock_[0], 1);
this->init ();
return result;
}
}
ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex (key_t k,
int flags,
int initial_value,
u_short nsems,
int perms)
{
ACE_TRACE ("ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex");
if (this->open (k, flags, initial_value, nsems, perms) == -1)
ACE_ERROR ((LM_ERROR, ACE_LIB_TEXT ("%p\n"), ACE_LIB_TEXT ("ACE_SV_Semaphore_Complex")));
}
ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex (const char *name,
int flags,
int initial_value,
u_short nsems,
int perms)
{
ACE_TRACE ("ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex");
key_t key;
if (name == 0)
key = ACE_DEFAULT_SEM_KEY;
else
key = this->name_2_key (name);
if (this->open (key, flags, initial_value, nsems, perms) == -1)
ACE_ERROR ((LM_ERROR, ACE_LIB_TEXT ("%p\n"), ACE_LIB_TEXT ("ACE_SV_Semaphore_Complex")));
}
ACE_SV_Semaphore_Complex::~ACE_SV_Semaphore_Complex (void)
{
ACE_TRACE ("ACE_SV_Semaphore_Complex::~ACE_SV_Semaphore_Complex");
if (this->internal_id_ >= 0)
this->close ();
}
ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex (void)
{
ACE_TRACE ("ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex");
this->init ();
}
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