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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 lock_object *lock" "const char *wmesg" "int flags" "int queue"
58 .Ft struct sleepqueue *
59 .Fn sleepq_alloc "void"
61 .Fn sleepq_broadcast "void *wchan" "int flags" "int pri" "int queue"
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" "int queue"
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 The implementation of each wait channel splits its sleepqueue into 2 sub-queues
95 in order to enable some optimizations on threads' wakeups.
96 An active queue holds a list of threads that are blocked on the associated
98 Threads that are not blocked on a wait channel have an associated inactive
100 When a thread blocks on a wait channel it donates its inactive sleep queue
102 When a thread is resumed,
103 the wait channel that it was blocked on gives it an inactive sleep queue for
108 function allocates an inactive sleep queue and is used to assign a
109 sleep queue to a thread during thread creation.
112 function frees the resources associated with an inactive sleep queue and is
113 used to free a queue during thread destruction.
115 Active sleep queues are stored in a hash table hashed on the addresses pointed
117 Each bucket in the hash table contains a sleep queue chain.
118 A sleep queue chain contains a spin mutex and a list of sleep queues that hash
119 to that specific chain.
120 Active sleep queues are protected by their chain's spin mutex.
123 function initializes the hash table of sleep queue chains.
127 function locks the sleep queue chain associated with wait channel
132 returns a pointer to the currently active sleep queue for that wait
133 channel associated with
137 if there is no active sleep queue associated with
140 It requires the sleep queue chain associated with
142 to have been locked by a prior call to
147 function unlocks the sleep queue chain associated with
149 and is primarily useful when aborting a pending sleep request before one of
150 the wait functions is called.
154 function places the current thread on the sleep queue associated with the
157 The sleep queue chain associated with argument
159 must be locked by a prior call to
161 when this function is called.
162 If a lock is specified via the
164 argument, and if the kernel was compiled with
165 .Cd "options INVARIANTS" ,
166 then the sleep queue code will perform extra checks to ensure that
167 the lock is used by all threads sleeping on
171 parameter should be a short description of
175 parameter is a bitmask consisting of the type of sleep queue being slept on
176 and zero or more optional flags.
179 parameter specifies the sub-queue, in which the contending thread will be
182 There are currently three types of sleep queues:
184 .Bl -tag -width ".Dv SLEEPQ_CONDVAR" -compact
185 .It Dv SLEEPQ_CONDVAR
186 A sleep queue used to implement condition variables.
188 A sleep queue used to implement
194 A sleep queue used to implement
198 There are currently two optional flag:
200 .Bl -tag -width ".Dv SLEEPQ_INTERRUPTIBLE" -compact
201 .It Dv SLEEPQ_INTERRUPTIBLE
202 The current thread is entering an interruptible sleep.
204 .Bl -tag -width ".Dv SLEEPQ_STOP_ON_BDRY" -compact
205 .It Dv SLEEPQ_STOP_ON_BDRY
206 When thread is entering an interruptible sleep, do not stop it upon
207 arrival of stop action, like
212 A timeout on the sleep may be specified by calling
213 .Fn sleepq_set_timeout
218 parameter should be the same value from the preceding call to
220 and the sleep queue chain associated with
222 must have been locked by a prior call to
226 parameter should specify the timeout value in ticks.
228 The current thread may be marked interruptible by calling
229 .Fn sleepq_catch_signals
232 set to the wait channel.
233 This function returns a signal number if there are any pending signals for
234 the current thread and 0 if there is not a pending signal.
235 The sleep queue chain associated with argument
237 should have been locked by a prior call to
240 Once the thread is ready to suspend,
241 one of the wait functions is called to put the current thread to sleep
242 until it is awakened and to context switch to another thread.
245 function is used for non-interruptible sleeps that do not have a timeout.
248 function is used for non-interruptible sleeps that have had a timeout set via
249 .Fn sleepq_set_timeout .
252 function is used for interruptible sleeps that do not have a timeout.
254 .Fn sleepq_timedwait_sig
255 function is used for interruptible sleeps that do have a timeout set.
258 argument to all of the wait functions is the wait channel being slept
260 The sleep queue chain associated with argument
262 needs to have been locked with a prior call to
267 .Fn sleepq_timedwait_sig
268 specifies if a previous call to
269 .Fn sleepq_catch_signals
270 found a pending signal.
272 When the thread is resumed,
273 the wait functions return a non-zero value if the thread was awakened due to
274 an interrupt other than a signal or a timeout.
275 If the sleep timed out, then
278 If the sleep was interrupted by something other than a signal,
279 then some other return value will be returned.
280 If zero is returned after resuming from an interruptible sleep,
282 .Fn sleepq_calc_signal_retval
283 should be called to determine if the sleep was interrupted by a signal.
285 .Fn sleepq_calc_signal_retval
288 if the interrupting signal is restartable and
291 If the sleep was not interrupted by a signal,
292 .Fn sleepq_calc_signal_retval
295 A sleeping thread is normally resumed by the
302 function awakens the highest priority thread sleeping on a wait channel while
304 awakens all of the threads sleeping on a wait channel.
307 argument specifics which wait channel to awaken.
310 argument must match the sleep queue type contained in the
314 by the threads sleeping on the wait channel.
317 argument does not equal \-1,
318 then each thread that is awakened will have its priority raised to
320 if it has a lower priority.
321 The sleep queue chain associated with argument
323 must be locked by a prior call to
325 before calling any of these functions.
328 argument specifies the sub-queue, from which threads need to be woken up.
330 A thread in an interruptible sleep can be interrupted by another thread via
336 argument specifies the thread to interrupt.
337 An individual thread can also be awakened from sleeping on a specific wait
343 argument specifies the thread to awaken and the
345 argument specifies the wait channel to awaken it from.
348 is not blocked on the the wait channel
350 then this function will not do anything,
351 even if the thread is asleep on a different wait channel.
352 This function should only be used if one of the other functions above is not
354 One possible use is waking up a specific thread from a widely shared sleep
359 .Fn sleepq_broadcast ,
362 functions all return a boolean value.
363 If the return value is true,
364 then at least one thread was resumed that is currently swapped out.
365 The caller is responsible for awakening the scheduler process so that the
366 resumed thread will be swapped back in.
367 This is done by calling the
369 function after releasing the sleep queue chain lock via a call to
372 The sleep queue interface is currently used to implement the
377 Almost all other code in the kernel should use one of those interfaces rather
378 than manipulating sleep queues directly.