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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 ,
44 .Fn KFAIL_POINT_CODE "parent" "name" "code"
45 .Fn KFAIL_POINT_RETURN "parent" "name"
46 .Fn KFAIL_POINT_RETURN_VOID "parent" "name"
47 .Fn KFAIL_POINT_ERROR "parent" "name" "error_var"
48 .Fn KFAIL_POINT_GOTO "parent" "name" "error_var" "label"
50 Fail points are used to add code points where errors may be injected
51 in a user controlled fashion.
52 Fail points provide a convenient wrapper around user-provided error
53 injection code, providing a
55 MIB, and a parser for that MIB that describes how the error
56 injection code should fire.
58 The base fail point macro is
62 is a sysctl tree (frequently
64 for kernel fail points, but various subsystems may wish to provide
65 their own fail point trees), and
67 is the name of the MIB in that tree, and
69 is the error injection code.
72 argument does not require braces, but it is considered good style to
73 use braces for any multi-line code arguments.
76 argument, the evaluation of
80 value set in the sysctl MIB.
87 macros are wrappers around common error injection paths:
89 .It Fn KFAIL_POINT_RETURN parent name
91 .Sy KFAIL_POINT_CODE(..., return RETURN_VALUE)
92 .It Fn KFAIL_POINT_RETURN_VOID parent name
94 .Sy KFAIL_POINT_CODE(..., return)
95 .It Fn KFAIL_POINT_ERROR parent name error_var
97 .Sy KFAIL_POINT_CODE(..., error_var = RETURN_VALUE)
98 .It Fn KFAIL_POINT_GOTO parent name error_var label
100 .Sy KFAIL_POINT_CODE(...,
101 { error_var = RETURN_VALUE; goto label;})
107 macros add sysctl MIBs where specified.
108 Many base kernel MIBs can be found in the
110 tree (referenced in code by
114 The sysctl variable may be set using the following grammar:
117 <term> ( "->" <term> )*
120 ( (<float> "%") | (<integer> "*" ) )*
122 [ "(" <integer> ")" ]
125 <integer> [ "." <integer> ] |
129 "off" | "return" | "sleep" | "panic" | "break" | "print"
132 argument specifies which action to take:
133 .Bl -tag -width ".Dv return"
135 Take no action (does not trigger fail point code)
137 Trigger fail point code with specified argument
139 Sleep the specified number of milliseconds
143 Break into the debugger, or trap if there is no debugger support
145 Print that the fail point executed
148 The <float>% and <integer>* modifiers prior to <type> control when
150 The <float>% form (e.g. "1.2%") can be used to specify a
151 probability that <type> will execute.
152 The <integer>* form (e.g. "5*") can be used to specify the number of
153 times <type> should be executed before this <term> is disabled.
154 Only the last probability and the last count are used if multiple
155 are specified, i.e. "1.2%2%" is the same as "2%".
156 When both a probability and a count are specified, the probability
157 is evaluated before the count, i.e. "2%5*" means "2% of the time,
158 but only 5 times total".
160 The operator -> can be used to express cascading terms.
161 If you specify <term1>-><term2>, it means that if <term1> doesn't
162 'execute', <term2> is evaluated.
163 For the purpose of this operator, the return() and print() operators
164 are the only types that cascade.
165 A return() term only cascades if the code executes, and a print()
166 term only cascades when passed a non-zero argument.
170 .It Sy sysctl debug.fail_point.foobar="2.1%return(5)"
171 21/1000ths of the time, execute
173 with RETURN_VALUE set to 5.
174 .It Sy sysctl debug.fail_point.foobar="2%return(5)->5%return(22)"
175 2/100ths of the time, execute
177 with RETURN_VALUE set to 5.
178 If that doesn't happen, 5% of the time execute
180 with RETURN_VALUE set to 22.
181 .It Sy sysctl debug.fail_point.foobar="5*return(5)->0.1%return(22)"
182 For 5 times, return 5.
183 After that, 1/1000th of the time, return 22.
184 .It Sy sysctl debug.fail_point.foobar="0.1%5*return(5)"
185 Return 5 for 1 in 1000 executions, but only 5 times total.
186 .It Sy sysctl debug.fail_point.foobar="1%*sleep(50)"
187 1/100th of the time, sleep 50ms.
191 It's easy to shoot yourself in the foot by setting fail points too
192 aggressively or setting too many in combination.
195 to fail consistently is potentially harmful to uptime.
199 sysctl setting may not be appropriate in all situations.
202 does not verify whether the context is appropriate for calling
207 This manual page was written by
208 .An Zach Loafman Aq zml@FreeBSD.org .