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36 .Nm sysctl_remove_oid ,
37 .Nm sysctl_remove_name
38 .Nd runtime sysctl tree manipulation
42 .Ft struct sysctl_oid *
44 .Fa "struct sysctl_ctx_list *ctx"
45 .Fa "struct sysctl_oid_list *parent"
47 .Fa "const char *name"
51 .Fa "int (*handler) (SYSCTL_HANDLER_ARGS)"
52 .Fa "const char *format"
53 .Fa "const char *descr"
57 .Fa "struct sysctl_oid *oidp"
58 .Fa "struct sysctl_oid_list *parent"
62 .Fa "struct sysctl_oid *oidp"
67 .Fo sysctl_remove_name
68 .Fa "struct sysctl_oid *oidp"
69 .Fa "const char *name"
74 These functions provide the interface for creating and deleting sysctl
75 OIDs at runtime for example during the lifetime of a module.
76 The wrapper macros defined by
78 are recommended when creating new OIDs.
80 should not be called directly from the code.
85 so that several code sections can create and delete them,
86 but in reality they are allocated and freed
87 based on their reference count.
89 it is possible for two or more code sections
90 to create partially overlapping trees that they both can use.
91 It is not possible to create overlapping leaves,
92 nor to create different child types with the same name and parent.
96 function creates a raw OID of any type and connects it to its parent node, if any.
97 If the OID is successfully created,
98 the function returns a pointer to it else
101 Many of the arguments for
103 are common to the wrapper macros defined by
108 function reparents an existing OID.
109 The OID is assigned a new number as if it had been created with
115 .Fn sysctl_remove_oid
116 function removes a dynamically created OID from the tree and
117 optionally freeing its resources.
118 It takes the following arguments:
119 .Bl -tag -width recurse
121 A pointer to the dynamic OID to be removed.
122 If the OID is not dynamic, or the pointer is
128 .Fn sysctl_remove_oid
129 will try to free the OID's resources
130 when the reference count of the OID becomes zero.
134 the routine will only deregister the OID from the tree,
135 without freeing its resources.
136 This behaviour is useful when the caller expects to rollback
137 (possibly partially failed)
138 deletion of many OIDs later.
140 If non-zero, attempt to remove the node and all its children.
144 any attempt to remove a node that contains any children
148 .Em WARNING : "use recursive deletion with extreme caution" !
149 Normally it should not be needed if contexts are used.
150 Contexts take care of tracking inter-dependencies
151 between users of the tree.
152 However, in some extreme cases it might be necessary
153 to remove part of the subtree no matter how it was created,
154 in order to free some other resources.
155 Be aware, though, that this may result in a system
157 if other code sections continue to use removed subtrees.
161 .Fn sysctl_remove_name
162 function looks up the child node matching the
164 argument and then invokes the
165 .Fn sysctl_remove_oid
166 function on that node, passing along the
171 If a node having the specified name does not exist an error code of
174 Else the error code from
175 .Fn sysctl_remove_oid
178 In most cases the programmer should use contexts,
180 .Xr sysctl_ctx_init 9 ,
181 to keep track of created OIDs,
182 and to delete them later in orderly fashion.
186 .Xr sysctl_ctx_free 9 ,
187 .Xr sysctl_ctx_init 9
189 These functions first appeared in
192 .An Andrzej Bialecki Aq Mt abial@FreeBSD.org
194 Sharing nodes between many code sections
195 causes interdependencies that sometimes may lock the resources.
197 if module A hooks up a subtree to an OID created by module B,
198 module B will be unable to delete that OID.
199 These issues are handled properly by sysctl contexts.
201 Many operations on the tree involve traversing linked lists.
202 For this reason, OID creation and removal is relatively costly.