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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"
54 .Fa "const char *label"
58 .Fa "struct sysctl_oid *oidp"
59 .Fa "struct sysctl_oid_list *parent"
63 .Fa "struct sysctl_oid *oidp"
68 .Fo sysctl_remove_name
69 .Fa "struct sysctl_oid *oidp"
70 .Fa "const char *name"
75 These functions provide the interface for creating and deleting sysctl
76 OIDs at runtime for example during the lifetime of a module.
77 The wrapper macros defined by
79 are recommended when creating new OIDs.
81 should not be called directly from the code.
86 so that several code sections can create and delete them,
87 but in reality they are allocated and freed
88 based on their reference count.
90 it is possible for two or more code sections
91 to create partially overlapping trees that they both can use.
92 It is not possible to create overlapping leaves,
93 nor to create different child types with the same name and parent.
97 function creates a raw OID of any type and connects it to its parent node, if any.
98 If the OID is successfully created,
99 the function returns a pointer to it else
102 Many of the arguments for
104 are common to the wrapper macros defined by
109 function reparents an existing OID.
110 The OID is assigned a new number as if it had been created with
116 .Fn sysctl_remove_oid
117 function removes a dynamically created OID from the tree and
118 optionally freeing its resources.
119 It takes the following arguments:
120 .Bl -tag -width recurse
122 A pointer to the dynamic OID to be removed.
123 If the OID is not dynamic, or the pointer is
129 .Fn sysctl_remove_oid
130 will try to free the OID's resources
131 when the reference count of the OID becomes zero.
135 the routine will only deregister the OID from the tree,
136 without freeing its resources.
137 This behaviour is useful when the caller expects to rollback
138 (possibly partially failed)
139 deletion of many OIDs later.
141 If non-zero, attempt to remove the node and all its children.
145 any attempt to remove a node that contains any children
149 .Em WARNING : "use recursive deletion with extreme caution" !
150 Normally it should not be needed if contexts are used.
151 Contexts take care of tracking inter-dependencies
152 between users of the tree.
153 However, in some extreme cases it might be necessary
154 to remove part of the subtree no matter how it was created,
155 in order to free some other resources.
156 Be aware, though, that this may result in a system
158 if other code sections continue to use removed subtrees.
162 .Fn sysctl_remove_name
163 function looks up the child node matching the
165 argument and then invokes the
166 .Fn sysctl_remove_oid
167 function on that node, passing along the
172 If a node having the specified name does not exist an error code of
175 Else the error code from
176 .Fn sysctl_remove_oid
179 In most cases the programmer should use contexts,
181 .Xr sysctl_ctx_init 9 ,
182 to keep track of created OIDs,
183 and to delete them later in orderly fashion.
187 .Xr sysctl_ctx_free 9 ,
188 .Xr sysctl_ctx_init 9
190 These functions first appeared in
193 .An Andrzej Bialecki Aq Mt abial@FreeBSD.org
195 Sharing nodes between many code sections
196 causes interdependencies that sometimes may lock the resources.
198 if module A hooks up a subtree to an OID created by module B,
199 module B will be unable to delete that OID.
200 These issues are handled properly by sysctl contexts.
202 Many operations on the tree involve traversing linked lists.
203 For this reason, OID creation and removal is relatively costly.