| 1.\" 2.\" Copyright (C) 2002 Chad David <davidc@acns.ab.ca>. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice(s), this list of conditions and the following disclaimer as --- 10 unchanged lines hidden (view full) --- 19.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 20.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 21.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 22.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 25.\" DAMAGE. 26.\" |
| 27.\" $FreeBSD: head/share/man/man9/lock.9 177962 2008-04-06 21:22:12Z attilio $ |
| 28.\" |
| 29.Dd April 6, 2008 |
| 30.Dt LOCK 9 31.Os 32.Sh NAME 33.Nm lockinit , 34.Nm lockdestroy , 35.Nm lockmgr , 36.Nm lockmgr_args , |
| 37.Nm lockmgr_args_rw , |
| 38.Nm lockmgr_disown , 39.Nm lockmgr_printinfo , 40.Nm lockmgr_recursed , |
| 41.Nm lockmgr_rw , |
| 42.Nm lockmgr_waiters , 43.Nm lockstatus , 44.Nm lockmgr_assert 45.Nd "lockmgr family of functions" 46.Sh SYNOPSIS 47.In sys/types.h 48.In sys/lock.h 49.In sys/lockmgr.h 50.Ft void 51.Fn lockinit "struct lock *lkp" "int prio" "const char *wmesg" "int timo" "int flags" 52.Ft void 53.Fn lockdestroy "struct lock *lkp" 54.Ft int |
| 55.Fn lockmgr "struct lock *lkp" "u_int flags" "struct mtx *ilk" |
| 56.Ft int |
| 57.Fn lockmgr_args "struct lock *lkp" "u_int flags" "struct mtx *ilk" "const char *wmesg" "int prio" "int timo" 58.Ft int 59.Fn lockmgr_args_rw "struct lock *lkp" "u_int flags" "struct rwlock *ilk" "const char *wmesg" "int prio" "int timo" |
| 60.Ft void 61.Fn lockmgr_disown "struct lock *lkp" 62.Ft void 63.Fn lockmgr_printinfo "struct lock *lkp" 64.Ft int 65.Fn lockmgr_recursed "struct lock *lkp" 66.Ft int |
| 67.Fn lockmgr_rw "struct lock *lkp" "u_int flags" "struct rwlock *ilk" 68.Ft int |
| 69.Fn lockmgr_waiters "struct lock *lkp" 70.Ft int 71.Fn lockstatus "struct lock *lkp" 72.Pp 73.Cd "options INVARIANTS" 74.Cd "options INVARIANT_SUPPORT" 75.Ft void 76.Fn lockmgr_assert "struct lock *lkp" "int what" --- 45 unchanged lines hidden (view full) --- 122.Pp 123The 124.Fn lockdestroy 125function is used to destroy a lock, and while it is called in a number of 126places in the kernel, it currently does nothing. 127.Pp 128The 129.Fn lockmgr |
| 130and 131.Fn lockmgr_rw 132functions handle general locking functionality within the kernel, including |
| 133support for shared and exclusive locks, and recursion. 134.Fn lockmgr |
| 135and 136.Fn lockmgr_rw 137are also able to upgrade and downgrade locks. |
| 138.Pp |
| 139Their arguments are: 140.Bl -tag -width ".Fa flags" |
| 141.It Fa lkp 142A pointer to the lock to manipulate. 143.It Fa flags 144Flags indicating what action is to be taken. 145.Bl -tag -width ".Dv LK_CANRECURSE" 146.It Dv LK_SHARED 147Acquire a shared lock. 148If an exclusive lock is currently held, it will be downgraded. --- 30 unchanged lines hidden (view full) --- 179Do not allow the call to sleep. 180This can be used to test the lock. 181.It Dv LK_CANRECURSE 182Allow recursion on an exclusive lock. 183For every lock there must be a release. 184.It Dv LK_INTERLOCK 185Unlock the interlock (which should be locked already). 186.El |
| 187.It Fa ilk |
| 188An interlock mutex for controlling group access to the lock. 189If 190.Dv LK_INTERLOCK 191is specified, 192.Fn lockmgr |
| 193and 194.Fn lockmgr_rw 195assume 196.Fa ilk |
| 197is currently owned and not recursed, and will return it unlocked. 198See 199.Xr mtx_assert 9 . 200.El 201.Pp 202The 203.Fn lockmgr_args |
| 204and 205.Fn lockmgr_args_rw 206function work like |
| 207.Fn lockmgr |
| 208and 209.Fn lockmgr_rw |
| 210but accepting a 211.Fa wmesg , 212.Fa timo 213and 214.Fa prio 215on a per-instance basis. 216The specified values will override the default 217ones, but this can still be used passing, respectively, --- 90 unchanged lines hidden (view full) --- 308usage is highly discouraged. 309They are intended to cater a bad behaviour 310introduced by buffer cache lock handling. 311They will hopefully be 312made useless by revisiting such locks. 313.Sh RETURN VALUES 314The 315.Fn lockmgr |
| 316and 317.Fn lockmgr_rw 318functions return 0 on success and non-zero on failure. |
| 319.Pp 320The 321.Fn lockstatus 322function returns: 323.Bl -tag -width ".Dv LK_EXCLUSIVE" 324.It Dv LK_EXCLUSIVE 325An exclusive lock is held by the current thread. 326.It Dv LK_EXCLOTHER 327An exclusive lock is held by someone other than the current thread. 328.It Dv LK_SHARED 329A shared lock is held. 330.It Li 0 331The lock is not held by anyone. 332.El 333.Sh ERRORS 334.Fn lockmgr |
| 335and 336.Fn lockmgr_rw 337fail if: |
| 338.Bl -tag -width Er 339.It Bq Er EBUSY 340.Dv LK_FORCEUPGRADE 341was requested and another thread had already requested a lock upgrade. 342.It Bq Er EBUSY 343.Dv LK_NOWAIT 344was set, and a sleep would have been required. 345.It Bq Er ENOLCK 346.Dv LK_SLEEPFAIL 347was set and 348.Fn lockmgr |
| 349or 350.Fn lockmgr_rw |
| 351did sleep. 352.It Bq Er EINTR 353.Dv PCATCH 354was set in the lock priority, and a signal was delivered during a sleep. 355Note the 356.Er ERESTART 357error below. 358.It Bq Er ERESTART --- 4 unchanged lines hidden (view full) --- 363a non-zero timeout was given, and the timeout expired. 364.El 365.Sh LOCKS 366If 367.Dv LK_INTERLOCK 368is passed in the 369.Fa flags 370argument to |
| 371.Fn lockmgr 372or 373.Fn lockmgr_rw , |
| 374the |
| 375.Fa ilk |
| 376must be held prior to calling |
| 377.Fn lockmgr 378or 379.Fn lockmgr_rw , |
| 380and will be returned unlocked. 381.Pp 382Upgrade attempts that fail result in the loss of the lock that 383is currently held. 384Also, it is invalid to upgrade an 385exclusive lock, and a 386.Xr panic 9 387will be the result of trying. --- 13 unchanged lines hidden --- |