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30 .Nm init_sleepqueues ,
34 .Nm sleepq_broadcast ,
35 .Nm sleepq_calc_signal_retval ,
36 .Nm sleepq_catch_signals ,
43 .Nm sleepq_set_timeout ,
44 .Nm sleepq_timedwait ,
45 .Nm sleepq_timedwait_sig ,
48 .Nd manage the queues of sleeping threads
53 .Fn init_sleepqueues "void"
55 .Fn sleepq_abort "struct thread *td"
57 .Fn sleepq_add "void *wchan" "struct mtx *lock" "const char *wmesg" "int flags"
58 .Ft struct sleepqueue *
59 .Fn sleepq_alloc "void"
61 .Fn sleepq_broadcast "void *wchan" "int flags" "int pri"
63 .Fn sleepq_calc_signal_retval "int sig"
65 .Fn sleepq_catch_signals "void *wchan"
67 .Fn sleepq_free "struct sleepqueue *sq"
68 .Ft struct sleepqueue *
69 .Fn sleepq_lookup "void *wchan"
71 .Fn sleepq_lock "void *wchan"
73 .Fn sleepq_release "void *wchan"
75 .Fn sleepq_remove "struct thread *td" "void *wchan"
77 .Fn sleepq_signal "void *wchan" "int flags" "int pri"
79 .Fn sleepq_set_timeout "void *wchan" "int timo"
81 .Fn sleepq_timedwait "void *wchan"
83 .Fn sleepq_timedwait_sig "void *wchan" "int signal_caught"
85 .Fn sleepq_wait "void *wchan"
87 .Fn sleepq_wait_sig "void *wchan"
89 Sleep queues provide a mechanism for suspending execution of a thread until
90 some condition is met.
91 Each queue is associated with a specific wait channel when it is active,
92 and only one queue may be associated with a wait channel at any given point
94 An active queue holds a list of threads that are blocked on the associated
96 Threads that are not blocked on a wait channel have an associated inactive
98 When a thread blocks on a wait channel it donates its inactive sleep queue
100 When a thread is resumed,
101 the wait channel that it was blocked on gives it an inactive sleep queue for
106 function allocates an inactive sleep queue and is used to assign a
107 sleep queue to a thread during thread creation.
110 function frees the resources associated with an inactive sleep queue and is
111 used to free a queue during thread destruction.
113 Active sleep queues are stored in a hash table hashed on the addresses pointed
115 Each bucket in the hash table contains a sleep queue chain.
116 A sleep queue chain contains a spin mutex and a list of sleep queues that hash
117 to that specific chain.
118 Active sleep queues are protected by their chain's spin mutex.
121 function initializes the hash table of sleep queue chains.
125 function locks the sleep queue chain associated with wait channel
130 returns a pointer to the currently active sleep queue for that wait
131 channel associated with
135 if there is no active sleep queue associated with
138 It requires the sleep queue chain associated with
140 to have been locked by a prior call to
145 function unlocks the sleep queue chain associated with
147 and is primarily useful when aborting a pending sleep request before one of
148 the wait functions is called.
152 function places the current thread on the sleep queue associated with the
155 The sleep queue chain associated with argument
157 must be locked by a prior call to
159 when this function is called.
160 If a mutex is specified via the
162 argument, and if the kernel was compiled with
163 .Cd "options INVARIANTS" ,
164 then the sleep queue code will perform extra checks to ensure that
165 the mutex is used by all threads sleeping on
169 parameter should be a short description of
173 parameter is a bitmask consisting of the type of sleep queue being slept on
174 and zero or more optional flags.
176 There are currently two types of sleep queues:
178 .Bl -tag -width ".Dv SLEEPQ_CONDVAR" -compact
179 .It Dv SLEEPQ_CONDVAR
180 A sleep queue used to implement condition variables.
182 A sleep queue used to implement
189 There is currently only one optional flag:
191 .Bl -tag -width ".Dv SLEEPQ_INTERRUPTIBLE" -compact
192 .It Dv SLEEPQ_INTERRUPTIBLE
193 The current thread is entering an interruptible sleep.
196 A timeout on the sleep may be specified by calling
197 .Fn sleepq_set_timeout
202 parameter should be the same value from the preceding call to
204 and the sleep queue chain associated with
206 must have been locked by a prior call to
210 parameter should specify the timeout value in ticks.
212 The current thread may be marked interruptible by calling
213 .Fn sleepq_catch_signals
216 set to the wait channel.
217 This function returns a signal number if there are any pending signals for
218 the current thread and 0 if there is not a pending signal.
219 The sleep queue chain associated with argument
221 should have been locked by a prior call to
224 Once the thread is ready to suspend,
225 one of the wait functions is called to put the current thread to sleep
226 until it is awakened and to context switch to another thread.
229 function is used for non-interruptible sleeps that do not have a timeout.
232 function is used for non-interruptible sleeps that have had a timeout set via
233 .Fn sleepq_set_timeout .
236 function is used for interruptible sleeps that do not have a timeout.
238 .Fn sleepq_timedwait_sig
239 function is used for interruptible sleeps that do have a timeout set.
242 argument to all of the wait functions is the wait channel being slept
244 The sleep queue chain associated with argument
246 needs to have been locked with a prior call to
251 .Fn sleepq_timedwait_sig
252 specifies if a previous call to
253 .Fn sleepq_catch_signals
254 found a pending signal.
256 When the thread is resumed,
257 the wait functions return a non-zero value if the thread was awakened due to
258 an interrupt other than a signal or a timeout.
259 If the sleep timed out, then
262 If the sleep was interrupted by something other than a signal,
263 then some other return value will be returned.
264 If zero is returned after resuming from an interruptible sleep,
266 .Fn sleepq_calc_signal_retval
267 should be called to determine if the sleep was interrupted by a signal.
269 .Fn sleepq_calc_signal_retval
272 if the interrupting signal is restartable and
275 If the sleep was not interrupted by a signal,
276 .Fn sleepq_calc_signal_retval
279 A sleeping thread is normally resumed by the
286 function awakens the highest priority thread sleeping on a wait channel while
288 awakens all of the threads sleeping on a wait channel.
291 argument specifics which wait channel to awaken.
294 argument must match the sleep queue type contained in the
298 by the threads sleeping on the wait channel.
301 argument does not equal \-1,
302 then each thread that is awakened will have its priority raised to
304 if it has a lower priority.
305 The sleep queue chain associated with argument
307 must be locked by a prior call to
309 before calling any of these functions.
311 A thread in an interruptible sleep can be interrupted by another thread via
317 argument specifies the thread to interrupt.
318 An individual thread can also be awakened from sleeping on a specific wait
324 argument specifies the thread to awaken and the
326 argument specifies the wait channel to awaken it from.
329 is not blocked on the the wait channel
331 then this function will not do anything,
332 even if the thread is asleep on a different wait channel.
333 This function should only be used if one of the other functions above is not
335 One possible use is waking up a specific thread from a widely shared sleep
338 The sleep queue interface is currently used to implement the
343 Almost all other code in the kernel should use one of those interfaces rather
344 than manipulating sleep queues directly.