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37 .Nd runtime sysctl tree manipulation
41 .Ft struct sysctl_oid *
43 .Fa "struct sysctl_ctx_list *ctx"
44 .Fa "struct sysctl_oid_list *parent"
46 .Fa "const char *name"
50 .Fa "int (*handler) (SYSCTL_HANDLER_ARGS)"
51 .Fa "const char *format"
52 .Fa "const char *descr"
56 .Fa "struct sysctl_oid *oidp"
57 .Fa "struct sysctl_oid_list *parent"
61 .Fa "struct sysctl_oid *oidp"
66 These functions provide the interface for creating and deleting sysctl
67 OIDs at runtime for example during the lifetime of a module.
68 The wrapper macros defined by
70 are recommended when creating new OIDs.
72 should not be called directly from the code.
77 so that several code sections can create and delete them,
78 but in reality they are allocated and freed
79 based on their reference count.
81 it is possible for two or more code sections
82 to create partially overlapping trees that they both can use.
83 It is not possible to create overlapping leaves,
84 nor to create different child types with the same name and parent.
88 function creates a raw OID of any type and connects it to its parent node, if any.
89 If the OID is successfully created,
90 the function returns a pointer to it else
93 Many of the arguments for
95 are common to the wrapper macros defined by
100 function reparents an existing OID.
101 The OID is assigned a new number as if it had been created with
107 .Fn sysctl_remove_oid
108 function removes a dynamically created OID from the tree and
109 optionally freeing its resources.
110 It takes the following arguments:
111 .Bl -tag -width recurse
113 A pointer to the dynamic OID to be removed.
114 If the OID is not dynamic, or the pointer is
120 .Fn sysctl_remove_oid
121 will try to free the OID's resources
122 when the reference count of the OID becomes zero.
126 the routine will only deregister the OID from the tree,
127 without freeing its resources.
128 This behaviour is useful when the caller expects to rollback
129 (possibly partially failed)
130 deletion of many OIDs later.
132 If non-zero, attempt to remove the node and all its children.
136 any attempt to remove a node that contains any children
140 .Em WARNING : "use recursive deletion with extreme caution" !
141 Normally it should not be needed if contexts are used.
142 Contexts take care of tracking inter-dependencies
143 between users of the tree.
144 However, in some extreme cases it might be necessary
145 to remove part of the subtree no matter how it was created,
146 in order to free some other resources.
147 Be aware, though, that this may result in a system
149 if other code sections continue to use removed subtrees.
152 Again, in most cases the programmer should use contexts,
154 .Xr sysctl_ctx_init 9 ,
155 to keep track of created OIDs,
156 and to delete them later in orderly fashion.
160 .Xr sysctl_ctx_free 9 ,
161 .Xr sysctl_ctx_init 9
163 These functions first appeared in
166 .An Andrzej Bialecki Aq Mt abial@FreeBSD.org
168 Sharing nodes between many code sections
169 causes interdependencies that sometimes may lock the resources.
171 if module A hooks up a subtree to an OID created by module B,
172 module B will be unable to delete that OID.
173 These issues are handled properly by sysctl contexts.
175 Many operations on the tree involve traversing linked lists.
176 For this reason, OID creation and removal is relatively costly.