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lock (9)
  • lock (1) ( FreeBSD man: Команды и прикладные программы пользовательского уровня )
  • lock (2) ( Русские man: Системные вызовы )
  • lock (2) ( Linux man: Системные вызовы )
  • lock (7) ( Linux man: Макропакеты и соглашения )
  • >> lock (9) ( FreeBSD man: Ядро )
  • Ключ lock обнаружен в базе ключевых слов.

  • BSD mandoc
     

    NAME

    
    
    lockinit
    
     
    lockdestroy
    
     
    lockcount
    
     
    lockmgr
    
     
    lockstatus
    
     
    lockmgr_printinfo
    
     - lockmgr family of functions
    
     
    

    SYNOPSIS

       #include <sys/types.h>
       #include <sys/lock.h>
       #include <sys/lockmgr.h>
    void lockinit (struct lock *lkp int prio const char *wmesg int timo int flags);
    void lockdestroy (struct lock *lkp);
    int lockcount (struct lock *lkp);
    int lockmgr (struct lock *lkp u_int flags struct mtx *interlkp struct thread *td);
    int lockstatus (struct lock *lkp struct thread *td);
    void lockmgr_printinfo (struct lock *lkp);
     

    DESCRIPTION

    The lockinit ();
    function is used to initialize a lock. It must be called before any operation can be performed on a lock. Its arguments are:

    Fa lkp
    A pointer to the lock to initialize.
    Fa prio
    The priority passed to sleep(9).
    Fa wmesg
    The lock message. This is used for both debugging output and sleep(9).
    Fa timo
    The timeout value passed to sleep(9).
    Fa flags
    The flags the lock is to be initialized with.

    LK_NOWAIT
    Do not sleep while acquiring the lock.
    LK_SLEEPFAIL
    Fail after a sleep.
    LK_CANRECURSE
    Allow recursive exclusive locks.
    LK_NOSHARE
    Allow exclusive locks only.
    LK_TIMELOCK
    Use Fa timo during a sleep; otherwise, 0 is used.

    The lockdestroy ();
    function is used to destroy a lock, and while it is called in a number of places in the kernel, it currently does nothing.

    The lockcount ();
    function returns a count of the number of exclusive locks and shared locks held against the lock Fa lkp .

    The lockmgr ();
    function handles general locking functionality within the kernel, including support for shared and exclusive locks, and recursion. lockmgr ();
    is also able to upgrade and downgrade locks.

    Its arguments are:

    Fa lkp
    A pointer to the lock to manipulate.
    Fa flags
    Flags indicating what action is to be taken.

    LK_SHARED
    Acquire a shared lock. If an exclusive lock is currently held, it will be downgraded.
    LK_EXCLUSIVE
    Acquire an exclusive lock. If an exclusive lock is already held, and LK_CANRECURSE is not set, the system will panic(9).
    LK_DOWNGRADE
    Downgrade exclusive lock to a shared lock. Downgrading a shared lock is not permitted. If an exclusive lock has been recursed, all references will be downgraded.
    LK_EXCLUPGRADE
    Upgrade a shared lock to an exclusive lock. Fails with Er EBUSY if there is someone ahead of you in line waiting for an upgrade. If this call fails, the shared lock is lost. Attempts to upgrade an exclusive lock will cause a panic(9).
    LK_UPGRADE
    Upgrade a shared lock to an exclusive lock. If this call fails, the shared lock is lost. During the upgrade, the shared lock could be temporarily dropped. Attempts to upgrade an exclusive lock will cause a panic(9).
    LK_RELEASE
    Release the lock. Releasing a lock that is not held can cause a panic(9).
    LK_DRAIN
    Wait for all activity on the lock to end, then mark it decommissioned. This is used before freeing a lock that is part of a piece of memory that is about to be freed. (As documented in In sys/lockmgr.h . )
    LK_SLEEPFAIL
    Fail if operation has slept.
    LK_NOWAIT
    Do not allow the call to sleep. This can be used to test the lock.
    LK_CANRECURSE
    Allow recursion on an exclusive lock. For every lock there must be a release.
    LK_INTERLOCK
    Unlock the interlock (which should be locked already).

    Fa interlkp
    An interlock mutex for controlling group access to the lock. If LK_INTERLOCK is specified, lockmgr ();
    assumes Fa interlkp is currently owned and not recursed, and will return it unlocked. See mtx_assert9.
    Fa td
    A thread responsible for this call. NULL becomes LK_KERNPROC

    The lockstatus ();
    function returns the status of the lock in relation to the Vt thread passed to it. Note that if Fa td is NULL and an exclusive lock is held, LK_EXCLUSIVE will be returned.

    The lockmgr_printinfo ();
    function prints debugging information about the lock. It is used primarily by VOP_PRINT9 functions.  

    RETURN VALUES

    The lockcount ();
    function returns an integer greater than or equal to zero.

    The lockmgr ();
    function returns 0 on success and non-zero on failure.

    The lockstatus ();
    function returns:

    LK_EXCLUSIVE
    An exclusive lock is held by the thread Fa td .
    LK_EXCLOTHER
    An exclusive lock is held by someone other than the thread Fa td .
    LK_SHARED
    A shared lock is held.
    0
    The lock is not held by anyone.

     

    ERRORS

    lockmgr ();
    fails if:

    Bq Er EBUSY
    LK_FORCEUPGRADE was requested and another thread had already requested a lock upgrade.
    Bq Er EBUSY
    LK_NOWAIT was set, and a sleep would have been required.
    Bq Er ENOLCK
    LK_SLEEPFAIL was set and lockmgr ();
    did sleep.
    Bq Er EINTR
    PCATCH was set in the lock priority, and a signal was delivered during a sleep. Note the Er ERESTART error below.
    Bq Er ERESTART
    PCATCH was set in the lock priority, a signal was delivered during a sleep, and the system call is to be restarted.
    Bq Er EWOULDBLOCK
    a non-zero timeout was given, and the timeout expired.

     

    LOCKS

    If LK_INTERLOCK is passed in the Fa flags argument to lockmgr (,);
    the Fa interlkp must be held prior to calling lockmgr (,);
    and will be returned unlocked.

    Upgrade attempts that fail result in the loss of the lock that is currently held. Also, it is invalid to upgrade an exclusive lock, and a panic(9) will be the result of trying.  

    SEE ALSO

    condvar(9), locking(9), mutex(9), rwlock(9), sleep(9), sx(9), mtx_assert9, panic(9), VOP_PRINT9  

    AUTHORS

    This manual page was written by An Chad David Aq davidc@acns.ab.ca .


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    ERRORS
    LOCKS
    SEE ALSO
    AUTHORS


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