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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 ,
45 .Nm sleepq_timedwait ,
46 .Nm sleepq_timedwait_sig ,
50 .Nd manage the queues of sleeping threads
55 .Fn init_sleepqueues "void"
57 .Fn sleepq_abort "struct thread *td"
59 .Fn sleepq_add "void *wchan" "struct lock_object *lock" "const char *wmesg" "int flags" "int queue"
60 .Ft struct sleepqueue *
61 .Fn sleepq_alloc "void"
63 .Fn sleepq_broadcast "void *wchan" "int flags" "int pri" "int queue"
65 .Fn sleepq_calc_signal_retval "int sig"
67 .Fn sleepq_catch_signals "void *wchan"
69 .Fn sleepq_free "struct sleepqueue *sq"
70 .Ft struct sleepqueue *
71 .Fn sleepq_lookup "void *wchan"
73 .Fn sleepq_lock "void *wchan"
75 .Fn sleepq_release "void *wchan"
77 .Fn sleepq_remove "struct thread *td" "void *wchan"
79 .Fn sleepq_signal "void *wchan" "int flags" "int pri" "int queue"
81 .Fn sleepq_set_timeout "void *wchan" "int timo"
83 .Fn sleepq_sleepcnt "void *wchan" "int queue"
85 .Fn sleepq_timedwait "void *wchan"
87 .Fn sleepq_timedwait_sig "void *wchan" "int signal_caught"
89 .Fn sleepq_type "void *wchan"
91 .Fn sleepq_wait "void *wchan"
93 .Fn sleepq_wait_sig "void *wchan"
95 Sleep queues provide a mechanism for suspending execution of a thread until
96 some condition is met.
97 Each queue is associated with a specific wait channel when it is active,
98 and only one queue may be associated with a wait channel at any given point
100 The implementation of each wait channel splits its sleepqueue into 2 sub-queues
101 in order to enable some optimizations on threads' wakeups.
102 An active queue holds a list of threads that are blocked on the associated
104 Threads that are not blocked on a wait channel have an associated inactive
106 When a thread blocks on a wait channel it donates its inactive sleep queue
108 When a thread is resumed,
109 the wait channel that it was blocked on gives it an inactive sleep queue for
114 function allocates an inactive sleep queue and is used to assign a
115 sleep queue to a thread during thread creation.
118 function frees the resources associated with an inactive sleep queue and is
119 used to free a queue during thread destruction.
121 Active sleep queues are stored in a hash table hashed on the addresses pointed
123 Each bucket in the hash table contains a sleep queue chain.
124 A sleep queue chain contains a spin mutex and a list of sleep queues that hash
125 to that specific chain.
126 Active sleep queues are protected by their chain's spin mutex.
129 function initializes the hash table of sleep queue chains.
133 function locks the sleep queue chain associated with wait channel
138 returns a pointer to the currently active sleep queue for that wait
139 channel associated with
143 if there is no active sleep queue associated with
146 It requires the sleep queue chain associated with
148 to have been locked by a prior call to
153 function unlocks the sleep queue chain associated with
155 and is primarily useful when aborting a pending sleep request before one of
156 the wait functions is called.
160 function places the current thread on the sleep queue associated with the
163 The sleep queue chain associated with argument
165 must be locked by a prior call to
167 when this function is called.
168 If a lock is specified via the
170 argument, and if the kernel was compiled with
171 .Cd "options INVARIANTS" ,
172 then the sleep queue code will perform extra checks to ensure that
173 the lock is used by all threads sleeping on
177 parameter should be a short description of
181 parameter is a bitmask consisting of the type of sleep queue being slept on
182 and zero or more optional flags.
185 parameter specifies the sub-queue, in which the contending thread will be
188 There are currently three types of sleep queues:
190 .Bl -tag -width ".Dv SLEEPQ_CONDVAR" -compact
191 .It Dv SLEEPQ_CONDVAR
192 A sleep queue used to implement condition variables.
194 A sleep queue used to implement
200 A sleep queue used to implement
204 There are currently two optional flag:
206 .Bl -tag -width ".Dv SLEEPQ_INTERRUPTIBLE" -compact
207 .It Dv SLEEPQ_INTERRUPTIBLE
208 The current thread is entering an interruptible sleep.
210 .Bl -tag -width ".Dv SLEEPQ_STOP_ON_BDRY" -compact
211 .It Dv SLEEPQ_STOP_ON_BDRY
212 When thread is entering an interruptible sleep, do not stop it upon
213 arrival of stop action, like
218 A timeout on the sleep may be specified by calling
219 .Fn sleepq_set_timeout
224 parameter should be the same value from the preceding call to
226 and the sleep queue chain associated with
228 must have been locked by a prior call to
232 parameter should specify the timeout value in ticks.
234 The current thread may be marked interruptible by calling
235 .Fn sleepq_catch_signals
238 set to the wait channel.
239 This function returns a signal number if there are any pending signals for
240 the current thread and 0 if there is not a pending signal.
241 The sleep queue chain associated with argument
243 should have been locked by a prior call to
246 Once the thread is ready to suspend,
247 one of the wait functions is called to put the current thread to sleep
248 until it is awakened and to context switch to another thread.
251 function is used for non-interruptible sleeps that do not have a timeout.
254 function is used for non-interruptible sleeps that have had a timeout set via
255 .Fn sleepq_set_timeout .
258 function is used for interruptible sleeps that do not have a timeout.
260 .Fn sleepq_timedwait_sig
261 function is used for interruptible sleeps that do have a timeout set.
264 argument to all of the wait functions is the wait channel being slept
266 The sleep queue chain associated with argument
268 needs to have been locked with a prior call to
273 .Fn sleepq_timedwait_sig
274 specifies if a previous call to
275 .Fn sleepq_catch_signals
276 found a pending signal.
278 When the thread is resumed,
279 the wait functions return a non-zero value if the thread was awakened due to
280 an interrupt other than a signal or a timeout.
281 If the sleep timed out, then
284 If the sleep was interrupted by something other than a signal,
285 then some other return value will be returned.
286 If zero is returned after resuming from an interruptible sleep,
288 .Fn sleepq_calc_signal_retval
289 should be called to determine if the sleep was interrupted by a signal.
291 .Fn sleepq_calc_signal_retval
294 if the interrupting signal is restartable and
297 If the sleep was not interrupted by a signal,
298 .Fn sleepq_calc_signal_retval
301 A sleeping thread is normally resumed by the
308 function awakens the highest priority thread sleeping on a wait channel while
310 awakens all of the threads sleeping on a wait channel.
313 argument specifics which wait channel to awaken.
316 argument must match the sleep queue type contained in the
320 by the threads sleeping on the wait channel.
323 argument does not equal \-1,
324 then each thread that is awakened will have its priority raised to
326 if it has a lower priority.
327 The sleep queue chain associated with argument
329 must be locked by a prior call to
331 before calling any of these functions.
334 argument specifies the sub-queue, from which threads need to be woken up.
336 A thread in an interruptible sleep can be interrupted by another thread via
342 argument specifies the thread to interrupt.
343 An individual thread can also be awakened from sleeping on a specific wait
349 argument specifies the thread to awaken and the
351 argument specifies the wait channel to awaken it from.
354 is not blocked on the the wait channel
356 then this function will not do anything,
357 even if the thread is asleep on a different wait channel.
358 This function should only be used if one of the other functions above is not
360 One possible use is waking up a specific thread from a widely shared sleep
365 function offer a simple way to retrieve the number of threads sleeping for
373 function returns the type of
375 associated to a sleepqueue.
379 .Fn sleepq_broadcast ,
382 functions all return a boolean value.
383 If the return value is true,
384 then at least one thread was resumed that is currently swapped out.
385 The caller is responsible for awakening the scheduler process so that the
386 resumed thread will be swapped back in.
387 This is done by calling the
389 function after releasing the sleep queue chain lock via a call to
392 The sleep queue interface is currently used to implement the
397 Almost all other code in the kernel should use one of those interfaces rather
398 than manipulating sleep queues directly.