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33 .Nm KFAIL_POINT_CODE ,
34 .Nm KFAIL_POINT_RETURN ,
35 .Nm KFAIL_POINT_RETURN_VOID ,
36 .Nm KFAIL_POINT_ERROR ,
37 .Nm KFAIL_POINT_GOTO ,
43 .Fn KFAIL_POINT_CODE "parent" "name" "code"
44 .Fn KFAIL_POINT_RETURN "parent" "name"
45 .Fn KFAIL_POINT_RETURN_VOID "parent" "name"
46 .Fn KFAIL_POINT_ERROR "parent" "name" "error_var"
47 .Fn KFAIL_POINT_GOTO "parent" "name" "error_var" "label"
49 Fail points are used to add code points where errors may be injected
50 in a user controlled fashion.
51 Fail points provide a convenient wrapper around user-provided error
52 injection code, providing a
54 MIB, and a parser for that MIB that describes how the error
55 injection code should fire.
57 The base fail point macro is
61 is a sysctl tree (frequently
63 for kernel fail points, but various subsystems may wish to provide
64 their own fail point trees), and
66 is the name of the MIB in that tree, and
68 is the error injection code.
71 argument does not require braces, but it is considered good style to
72 use braces for any multi-line code arguments.
75 argument, the evaluation of
79 value set in the sysctl MIB.
86 macros are wrappers around common error injection paths:
88 .It Fn KFAIL_POINT_RETURN parent name
90 .Sy KFAIL_POINT_CODE(..., return RETURN_VALUE)
91 .It Fn KFAIL_POINT_RETURN_VOID parent name
93 .Sy KFAIL_POINT_CODE(..., return)
94 .It Fn KFAIL_POINT_ERROR parent name error_var
96 .Sy KFAIL_POINT_CODE(..., error_var = RETURN_VALUE)
97 .It Fn KFAIL_POINT_GOTO parent name error_var label
99 .Sy KFAIL_POINT_CODE(...,
100 { error_var = RETURN_VALUE; goto label;})
105 macros add sysctl MIBs where specified.
106 Many base kernel MIBs can be found in the
108 tree (referenced in code by
111 The sysctl variable may be set using the following grammar:
115 <term> ( "->" <term> )*
118 ( (<float> "%") | (<integer> "*" ) )*
120 [ "(" <integer> ")" ]
123 <integer> [ "." <integer> ] |
127 "off" | "return" | "sleep" | "panic" | "break" | "print"
130 The <type> argument specifies which action to take:
131 .Bl -tag -width ".Dv return"
133 Take no action (does not trigger fail point code)
135 Trigger fail point code with specified argument
137 Sleep the specified number of milliseconds
141 Break into the debugger, or trap if there is no debugger support
143 Print that the fail point executed
146 The <float>% and <integer>* modifiers prior to <type> control when
148 The <float>% form (e.g. "1.2%") can be used to specify a
149 probability that <type> will execute.
150 The <integer>* form (e.g. "5*") can be used to specify the number of
151 times <type> should be executed before this <term> is disabled.
152 Only the last probability and the last count are used if multiple
153 are specified, i.e. "1.2%2%" is the same as "2%".
154 When both a probability and a count are specified, the probability
155 is evaluated before the count, i.e. "2%5*" means "2% of the time,
156 but only 5 times total".
158 The operator -> can be used to express cascading terms.
159 If you specify <term1>-><term2>, it means that if <term1> does not
161 <term2> is evaluated.
162 For the purpose of this operator, the return() and print() operators
163 are the only types that cascade.
164 A return() term only cascades if the code executes, and a print()
165 term only cascades when passed a non-zero argument.
168 .It Sy sysctl debug.fail_point.foobar="2.1%return(5)"
169 21/1000ths of the time, execute
171 with RETURN_VALUE set to 5.
172 .It Sy sysctl debug.fail_point.foobar="2%return(5)->5%return(22)"
173 2/100ths of the time, execute
175 with RETURN_VALUE set to 5.
176 If that does not happen, 5% of the time execute
178 with RETURN_VALUE set to 22.
179 .It Sy sysctl debug.fail_point.foobar="5*return(5)->0.1%return(22)"
180 For 5 times, return 5.
181 After that, 1/1000th of the time, return 22.
182 .It Sy sysctl debug.fail_point.foobar="0.1%5*return(5)"
183 Return 5 for 1 in 1000 executions, but only 5 times total.
184 .It Sy sysctl debug.fail_point.foobar="1%*sleep(50)"
185 1/100th of the time, sleep 50ms.
188 It is easy to shoot yourself in the foot by setting fail points too
189 aggressively or setting too many in combination.
192 to fail consistently is potentially harmful to uptime.
196 sysctl setting may not be appropriate in all situations.
199 does not verify whether the context is appropriate for calling
203 This manual page was written by
204 .An Zach Loafman Aq zml@FreeBSD.org .