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39 .Nm lockmgr_printinfo ,
40 .Nm lockmgr_recursed ,
45 .Nd "lockmgr family of functions"
51 .Fn lockinit "struct lock *lkp" "int prio" "const char *wmesg" "int timo" "int flags"
53 .Fn lockdestroy "struct lock *lkp"
55 .Fn lockmgr "struct lock *lkp" "u_int flags" "struct mtx *ilk"
57 .Fn lockmgr_args "struct lock *lkp" "u_int flags" "struct mtx *ilk" "const char *wmesg" "int prio" "int timo"
59 .Fn lockmgr_args_rw "struct lock *lkp" "u_int flags" "struct rwlock *ilk" "const char *wmesg" "int prio" "int timo"
61 .Fn lockmgr_disown "struct lock *lkp"
63 .Fn lockmgr_printinfo "struct lock *lkp"
65 .Fn lockmgr_recursed "struct lock *lkp"
67 .Fn lockmgr_rw "struct lock *lkp" "u_int flags" "struct rwlock *ilk"
69 .Fn lockmgr_waiters "struct lock *lkp"
71 .Fn lockstatus "struct lock *lkp"
73 .Cd "options INVARIANTS"
74 .Cd "options INVARIANT_SUPPORT"
76 .Fn lockmgr_assert "struct lock *lkp" "int what"
80 function is used to initialize a lock.
81 It must be called before any operation can be performed on a lock.
83 .Bl -tag -width ".Fa wmesg"
85 A pointer to the lock to initialize.
87 The priority passed to
91 This is used for both debugging output and
94 The timeout value passed to
97 The flags the lock is to be initialized with:
98 .Bl -tag -width ".Dv LK_CANRECURSE"
100 Allow recursive exclusive locks.
102 Disable lock profiling for this lock.
104 Allow exclusive locks only.
111 should log messages about duplicate locks being acquired.
115 logging for this lock.
119 during a sleep; otherwise, 0 is used.
125 function is used to destroy a lock, and while it is called in a number of
126 places in the kernel, it currently does nothing.
132 functions handle general locking functionality within the kernel, including
133 support for shared and exclusive locks, and recursion.
137 are also able to upgrade and downgrade locks.
140 .Bl -tag -width ".Fa flags"
142 A pointer to the lock to manipulate.
144 Flags indicating what action is to be taken.
145 .Bl -tag -width ".Dv LK_CANRECURSE"
147 Acquire a shared lock.
148 If an exclusive lock is currently held, it will be downgraded.
150 Acquire an exclusive lock.
151 If an exclusive lock is already held, and
153 is not set, the system will
156 Downgrade exclusive lock to a shared lock.
157 Downgrading a shared lock is not permitted.
158 If an exclusive lock has been recursed, all references will be downgraded.
160 Upgrade a shared lock to an exclusive lock.
161 If this call fails, the shared lock is lost.
162 During the upgrade, the shared lock could
163 be temporarily dropped.
164 Attempts to upgrade an exclusive lock will cause a
168 Releasing a lock that is not held can cause a
171 Wait for all activity on the lock to end, then mark it decommissioned.
172 This is used before freeing a lock that is part of a piece of memory that is
175 .In sys/lockmgr.h . )
177 Fail if operation has slept.
179 Do not allow the call to sleep.
180 This can be used to test the lock.
184 checks for this instance.
186 Allow recursion on an exclusive lock.
187 For every lock there must be a release.
189 Unlock the interlock (which should be locked already).
192 An interlock mutex for controlling group access to the lock.
201 is currently owned and not recursed, and will return it unlocked.
219 on a per-instance basis.
220 The specified values will override the default
221 ones, but this can still be used passing, respectively,
222 .Dv LK_WMESG_DEFAULT ,
225 .Dv LK_TIMO_DEFAULT .
229 function switches the owner from the current thread to be
231 if the lock is already held.
234 .Fn lockmgr_printinfo
235 function prints debugging information about the lock.
236 It is used primarily by
242 function returns true if the lock is recursed, 0
247 function returns true if the lock has waiters, 0 otherwise.
251 function returns the status of the lock in relation to the current thread.
254 .Cd "options INVARIANTS"
256 .Cd "options INVARIANT_SUPPORT" ,
261 for the assertions specified in
263 and panics if they are not met.
264 One of the following assertions must be specified:
265 .Bl -tag -width ".Dv KA_UNLOCKED"
267 Assert that the current thread has either a shared or an exclusive lock on the
269 lock pointed to by the first argument.
271 Assert that the current thread has a shared lock on the
273 lock pointed to by the first argument.
275 Assert that the current thread has an exclusive lock on the
277 lock pointed to by the first argument.
279 Assert that the current thread has no lock on the
281 lock pointed to by the first argument.
283 Assert that an unspecified thread has a lock on the
285 lock pointed to by the first argument.
287 Assert that no thread has a lock on the
289 lock pointed to by the first argument.
292 In addition, one of the following optional assertions can be used with
299 .Bl -tag -width ".Dv KA_NOTRECURSED"
301 Assert that the current thread has a recursed lock on
303 .It Dv KA_NOTRECURSED
304 Assert that the current thread does not have a recursed lock on
312 usage is highly discouraged.
313 They are intended to cater a bad behaviour
314 introduced by buffer cache lock handling.
315 They will hopefully be
316 made useless by revisiting such locks.
322 functions return 0 on success and non-zero on failure.
327 .Bl -tag -width ".Dv LK_EXCLUSIVE"
329 An exclusive lock is held by the current thread.
331 An exclusive lock is held by someone other than the current thread.
333 A shared lock is held.
335 The lock is not held by anyone.
345 was requested and another thread had already requested a lock upgrade.
348 was set, and a sleep would have been required.
358 was set in the lock priority, and a signal was delivered during a sleep.
364 was set in the lock priority, a signal was delivered during a sleep,
365 and the system call is to be restarted.
366 .It Bq Er EWOULDBLOCK
367 a non-zero timeout was given, and the timeout expired.
380 must be held prior to calling
384 and will be returned unlocked.
386 Upgrade attempts that fail result in the loss of the lock that
388 Also, it is invalid to upgrade an
389 exclusive lock, and a
391 will be the result of trying.
403 This manual page was written by
404 .An Chad David Aq davidc@acns.ab.ca .