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OpenSolaris 2009.06 - man page for semtimedop (opensolaris section 2)

semop(2)				   System Calls 				 semop(2)

NAME
       semop, semtimedop - semaphore operations

SYNOPSIS
       #include <sys/types.h>
       #include <sys/ipc.h>
       #include <sys/sem.h>

       int semop(int semid, struct sembuf *sops, size_t nsops);

       int semtimedop(int semid, struct sembuf *sops, size_t nsops,
	    const struct timespec *timeout);

DESCRIPTION
       The semop() function is used to perform atomically an array of semaphore operations on the
       set of semaphores associated with the semaphore identifier specified by	semid.	The  sops
       argument  is  a pointer to the array of semaphore-operation structures. The nsops argument
       is the number of such structures in the array.

       Each sembuf structure contains the following members:

	 short	   sem_num;    /* semaphore number */
	 short	   sem_op;     /* semaphore operation */
	 short	   sem_flg;    /* operation flags */

       Each semaphore operation specified by sem_op is performed on the  corresponding	semaphore
       specified by semid and sem_num. The permission required for a semaphore operation is given
       as {token}, where token is the type of permission needed.  The  types  of  permission  are
       interpreted as follows:

	 00400	  READ by user
	 00200	  ALTER by user
	 00040	  READ by group
	 00020	  ALTER by group
	 00004	  READ by others
	 00002	  ALTER by others

       See the Semaphore Operation Permissions section of Intro(2) for more information.

       A  process  maintains a value, semadj, for each semaphore it modifies. This value contains
       the cumulative effect of operations the process has performed on an  individual	semaphore
       with the SEM_UNDO flag set (so that they can be undone if the process terminates unexpect-
       edly).  The value of semadj can affect the behavior of  calls  to  semop(),  semtimedop(),
       exit(),	and  _exit()  (the  latter two functions documented on exit(2)), but is otherwise
       unobservable. See below for details.

       The sem_op member specifies one of three semaphore operations:

	   1.	  The sem_op member is a negative integer; {ALTER}

	       o      If semval (see Intro(2)) is greater than or equal to the absolute value  of
		      sem_op,  the  absolute  value of sem_op is subtracted from semval. Also, if
		      (sem_flg&SEM_UNDO) is true, the absolute value of sem_op is  added  to  the
		      calling process's semadj value (see exit(2)) for the specified semaphore.

	       o      If   semval   is	 less	than   the   absolute	value	of   sem_op   and
		      (sem_flg&IPC_NOWAIT) is true, semop() returns immediately.

	       o      If   semval   is	 less	than   the   absolute	value	of   sem_op   and
		      (sem_flg&IPC_NOWAIT)  is	false,	semop() increments the semncnt associated
		      with the specified semaphore and suspends execution of the  calling  thread
		      until one of the following conditions occur:

		   o	  The value of semval becomes greater than or equal to the absolute value
			  of sem_op. When this occurs, the value of semncnt associated	with  the
			  specified  semaphore	is  decremented,  the absolute value of sem_op is
			  subtracted from semval and, if (sem_flg&SEM_UNDO) is true, the absolute
			  value  of sem_op is added to the calling process's semadj value for the
			  specified semaphore.

		   o	  The semid for which the calling thread is awaiting  action  is  removed
			  from	the  system  (see  semctl(2)).	When this occurs, errno is set to
			  EIDRM and -1 is returned.

		   o	  The calling thread receives a signal that is to be  caught.  When  this
			  occurs, the value of semncnt associated with the specified semaphore is
			  decremented, and the calling thread resumes  execution  in  the  manner
			  prescribed in sigaction(2).

	   2.	  The sem_op member is a positive integer; {ALTER}

		  The  value of sem_op is added to semval and, if (sem_flg&SEM_UNDO) is true, the
		  value of sem_op is subtracted from the calling process's semadj value  for  the
		  specified semaphore.

	   3.	  The sem_op member is 0; {READ}

	       o      If semval is 0, semop() returns immediately.

	       o      If  semval  is  not  equal  to  0 and (sem_flg&IPC_NOWAIT) is true, semop()
		      returns immediately.

	       o      If semval is not equal to 0  and	(sem_flg&IPC_NOWAIT)  is  false,  semop()
		      increments the semzcnt associated with the specified semaphore and suspends
		      execution of the calling thread until one of the following occurs:

		   o	  The value of semval becomes 0, at which time the value of semzcnt asso-
			  ciated with the specified semaphore is set to 0 and all processes wait-
			  ing on semval to become 0 are awakened.

		   o	  The semid for which the calling thread is awaiting  action  is  removed
			  from	the  system.  When  this  occurs, errno is set to EIDRM and -1 is
			  returned.

		   o	  The calling thread receives a signal that is to be  caught.  When  this
			  occurs, the value of semzcnt associated with the specified semaphore is
			  decremented, and the calling thread resumes  execution  in  the  manner
			  prescribed in sigaction(2).

       Upon  successful completion, the value of sempid for each semaphore specified in the array
       pointed to by sops is set to the process ID of the calling process.

       The semtimedop() function behaves as semop() except when it must suspend execution of  the
       calling	process  to  complete  its  operation.	 If semtimedop() must suspend the calling
       process after the time interval specified in timeout expires, or if  the  timeout  expires
       while the process is suspended, semtimedop() returns with an error. If the timespec struc-
       ture pointed to by timeout is zero-valued and semtimedop() needs to  suspend  the  calling
       process	to  complete the requested operation(s), it returns immediately with an error. If
       timeout is the NULL pointer, the behavior of semtimedop() is identical to that of semop().

RETURN VALUES
       Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is  set  to
       indicate the error.

ERRORS
       The semop() and semtimedop() functions will fail if:

       E2BIG	 The nsops argument is greater than the system-imposed maximum. See NOTES.

       EACCES	 Operation permission is denied to the calling process (see Intro(2)).

       EAGAIN	 The   operation   would   result  in  suspension  of  the  calling  process  but
		 (sem_flg&IPC_NOWAIT) is true.

       EFAULT	 The sops argument points to an illegal address.

       EFBIG	 The value of sem_num is less than 0 or greater than or equal to  the  number  of
		 semaphores in the set associated with semid.

       EIDRM	 A semid was removed from the system.

       EINTR	 A signal was received.

       EINVAL	 The  semid  argument is not a valid semaphore identifier, or the number of indi-
		 vidual semaphores for which the calling process requests  a  SEM_UNDO	operation
		 would	exceed	the  system-imposed limit. Solaris does not impose a limit on the
		 number of individual  semaphores  for	which  the  calling  process  requests	a
		 SEM_UNDO operation.

       ENOSPC	 The  limit on the number of individual processes requesting a SEM_UNDO operation
		 would be exceeded. Solaris does not impose a limit on the number  of  individual
		 processes requesting an SEM_UNDO operation.

       ERANGE	 An  operation	would  cause  a  semval or a semadj value to overflow the system-
		 imposed limit.

       The semtimedop() function will fail if:

       EAGAIN	 The timeout expired before the requested operation could be completed.

       The semtimedop() function will fail if one of the following is detected:

       EFAULT	 The timeout argument points to an illegal address.

       EINVAL	 The timeout argument specified a tv_sec or tv_nsec  value  less  than	0,  or	a
		 tv_nsec value greater than or equal to 1000 million.

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |semop() is Standard.	   |
       +-----------------------------+-----------------------------+

SEE ALSO
       ipcs(1),   rctladm(1M),	 Intro(2),   exec(2),  exit(2),  fork(2),  semctl(2),  semget(2),
       setrctl(2), sigaction(2), attributes(5), standards(5)

NOTES
       The system-imposed maximum on nsops for a semaphore identifier  is  the	minimum  enforced
       value  of  the  process.max-sem-ops  resource  control of the creating process at the time
       semget(2) was used to allocate the identifier.

       See rctladm(1M) and setrctl(2) for information about using resource controls.

SunOS 5.11				   12 May 2006					 semop(2)


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