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39 .Nm lockmgr_printinfo ,
40 .Nm lockmgr_recursed ,
44 .Nd "lockmgr family of functions"
50 .Fn lockinit "struct lock *lkp" "int prio" "const char *wmesg" "int timo" "int flags"
52 .Fn lockdestroy "struct lock *lkp"
54 .Fn lockmgr "struct lock *lkp" "u_int flags" "struct mtx *ilk"
56 .Fn lockmgr_args "struct lock *lkp" "u_int flags" "struct mtx *ilk" "const char *wmesg" "int prio" "int timo"
58 .Fn lockmgr_args_rw "struct lock *lkp" "u_int flags" "struct rwlock *ilk" "const char *wmesg" "int prio" "int timo"
60 .Fn lockmgr_disown "struct lock *lkp"
62 .Fn lockmgr_printinfo "const struct lock *lkp"
64 .Fn lockmgr_recursed "const struct lock *lkp"
66 .Fn lockmgr_rw "struct lock *lkp" "u_int flags" "struct rwlock *ilk"
68 .Fn lockstatus "const struct lock *lkp"
70 .Cd "options INVARIANTS"
71 .Cd "options INVARIANT_SUPPORT"
73 .Fn lockmgr_assert "const struct lock *lkp" "int what"
77 function is used to initialize a lock.
78 It must be called before any operation can be performed on a lock.
80 .Bl -tag -width ".Fa wmesg"
82 A pointer to the lock to initialize.
84 The priority passed to
88 This is used for both debugging output and
91 The timeout value passed to
94 The flags the lock is to be initialized with:
95 .Bl -tag -width ".Dv LK_CANRECURSE"
97 Allow recursive exclusive locks.
99 Disable lock profiling for this lock.
101 Allow exclusive locks only.
108 should log messages about duplicate locks being acquired.
112 logging for this lock.
116 during a sleep; otherwise, 0 is used.
122 function is used to destroy a lock, and while it is called in a number of
123 places in the kernel, it currently does nothing.
129 functions handle general locking functionality within the kernel, including
130 support for shared and exclusive locks, and recursion.
134 are also able to upgrade and downgrade locks.
137 .Bl -tag -width ".Fa flags"
139 A pointer to the lock to manipulate.
141 Flags indicating what action is to be taken.
142 .Bl -tag -width ".Dv LK_NODDLKTREAT"
144 Acquire a shared lock.
145 If an exclusive lock is currently held,
149 Acquire an exclusive lock.
150 If an exclusive lock is already held, and
152 is not set, the system will
155 Downgrade exclusive lock to a shared lock.
156 Downgrading a shared lock is not permitted.
157 If an exclusive lock has been recursed, the system will
160 Upgrade a shared lock to an exclusive lock.
161 If this call fails, the shared lock is lost, even if the
164 During the upgrade, the shared lock could
165 be temporarily dropped.
166 Attempts to upgrade an exclusive lock will cause a
169 Try to upgrade a shared lock to an exclusive lock.
170 The failure to upgrade does not result in the dropping
171 of the shared lock ownership.
174 Releasing a lock that is not held can cause a
177 Wait for all activity on the lock to end, then mark it decommissioned.
178 This is used before freeing a lock that is part of a piece of memory that is
181 .In sys/lockmgr.h . )
183 Fail if operation has slept.
185 Do not allow the call to sleep.
186 This can be used to test the lock.
190 checks for this instance.
192 Allow recursion on an exclusive lock.
193 For every lock there must be a release.
195 Unlock the interlock (which should be locked already).
196 .It Dv LK_NODDLKTREAT
199 postpones serving further shared requests for shared-locked lock if there is
200 exclusive waiter, to avoid exclusive lock starvation.
201 But, if the thread requesting the shared lock already owns a shared lockmgr
202 lock, the request is granted even in presence of the parallel exclusive lock
203 request, which is done to avoid deadlocks with recursive shared acquisition.
207 flag can only be used by code which requests shared non-recursive lock.
208 The flag allows exclusive requests to preempt the current shared request
209 even if the current thread owns shared locks.
210 This is safe since shared lock is guaranteed to not recurse, and is used
211 when thread is known to held unrelated shared locks, to not cause
212 unnecessary starvation.
222 An interlock mutex for controlling group access to the lock.
231 is currently owned and not recursed, and will return it unlocked.
249 on a per-instance basis.
250 The specified values will override the default
251 ones, but this can still be used passing, respectively,
252 .Dv LK_WMESG_DEFAULT ,
255 .Dv LK_TIMO_DEFAULT .
259 function switches the owner from the current thread to be
261 if the lock is already held.
264 .Fn lockmgr_printinfo
265 function prints debugging information about the lock.
266 It is used primarily by
272 function returns true if the lock is recursed, 0
277 function returns the status of the lock in relation to the current thread.
280 .Cd "options INVARIANTS"
282 .Cd "options INVARIANT_SUPPORT" ,
287 for the assertions specified in
289 and panics if they are not met.
290 One of the following assertions must be specified:
291 .Bl -tag -width ".Dv KA_UNLOCKED"
293 Assert that the current thread has either a shared or an exclusive lock on the
295 lock pointed to by the first argument.
297 Assert that the current thread has a shared lock on the
299 lock pointed to by the first argument.
301 Assert that the current thread has an exclusive lock on the
303 lock pointed to by the first argument.
305 Assert that the current thread has no lock on the
307 lock pointed to by the first argument.
310 In addition, one of the following optional assertions can be used with
317 .Bl -tag -width ".Dv KA_NOTRECURSED"
319 Assert that the current thread has a recursed lock on
321 .It Dv KA_NOTRECURSED
322 Assert that the current thread does not have a recursed lock on
330 functions return 0 on success and non-zero on failure.
335 .Bl -tag -width ".Dv LK_EXCLUSIVE"
337 An exclusive lock is held by the current thread.
339 An exclusive lock is held by someone other than the current thread.
341 A shared lock is held.
343 The lock is not held by anyone.
353 was requested and another thread had already requested a lock upgrade.
356 was set, and a sleep would have been required, or
358 operation was not able to upgrade the lock.
368 was set in the lock priority, and a signal was delivered during a sleep.
374 was set in the lock priority, a signal was delivered during a sleep,
375 and the system call is to be restarted.
376 .It Bq Er EWOULDBLOCK
377 a non-zero timeout was given, and the timeout expired.
390 must be held prior to calling
394 and will be returned unlocked.
396 Upgrade attempts that fail result in the loss of the lock that
398 Also, it is invalid to upgrade an
399 exclusive lock, and a
401 will be the result of trying.
413 This manual page was written by
414 .An Chad David Aq Mt davidc@acns.ab.ca .