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26 .\" $FreeBSD: src/share/man/man9/sleep.9,v 1.18.2.5 2001/12/17 11:30:19 ru Exp $
27 .\" $DragonFly: src/share/man/man9/sleep.9,v 1.2 2003/06/17 04:37:01 dillon Exp $
44 .Fn tsleep "void *ident" "int priority" "const char *wmesg" "int timo"
46 .Fn asleep "void *ident" "int priority" "const char *wmesg" "int timo"
48 .Fn await "int priority" "int timo"
50 .Fn wakeup "void *ident"
52 .Fn wakeup_one "void *ident"
58 handle event-based process blocking. If a process must wait for an
59 external event, it is put on sleep by
63 is an arbitrary address that uniquely identifies the event on which
64 the process is being asleep. All processes sleeping on a single
68 often called from inside an interrupt routine, to indicate that the
69 resource the process was blocking on is available now.
73 is a string describing the sleep condition for tools like
75 Due to the limited space of those programs to display arbitrary strings,
76 this message should not be longer than 6 characters.
80 function is used to make the first process in the queue that is
81 sleeping on the parameter
83 runnable. This can prevent the system from becoming saturated
84 when a large number of processes are sleeping on the same address,
85 but only one of them can actually do any useful work when made
89 is the general sleep call. Suspends the current process until a wakeup is
90 performed on the specified identifier. The process will then be made
91 runnable with the specified
95 \&/ hz seconds (0 means no timeout). If
99 flag, signals are checked before and after sleeping, else signals are
100 not checked. Returns 0 if awakened,
102 if the timeout expires. If
104 is set and a signal needs to be delivered,
106 is returned if the current system call should be restarted if
109 is returned if the system call should be interrupted by the signal
114 implements the new asynchronous sleep function. It takes the same arguments
117 and places the process on the appropriate wait queue, but
119 leaves the process runnable and returns immediately. The caller is then
120 expected to, at some point in the future, call
122 to actually wait for the previously queued wait condition.
125 is called several times, only the most recent call is effective.
127 may be called with an
130 to remove any previously queued condition.
133 implements the new asynchronous wait function. When
135 is called on an identifier it associates the process with that
136 identifier but does not block.
138 will actually block the process until
140 is called on that identifier any time after the
150 call is effectively a NOP.
153 is called multiple times without an intervening
157 is effectively a NOP but will also call
161 function allows you to override the priority and timeout values to be used.
162 If the value -1 is specified for an argument, the value is taken from the
165 call. If -1 is passed for the priority you must be prepared to catch signal
166 conditions if the prior call to
168 specified it in its priority. If -1 is passed for the timeout you must be
169 prepared to catch a timeout condition if the prior call to
171 specified a timeout. When you use -1, it is usually a good idea to not make
172 assumptions as to the arguments used by the prior
180 functions are mainly used by the kernel to shift the burden of blocking
181 away from extremely low level routines and to push it onto their callers.
182 This in turn allows more complex interlocking code to
184 of a temporary resource failure
185 (such as lack of memory) in order to release major locks prior to actually
186 blocking, and to then retry the operation on wakeup. This key feature is
187 expected to be heavily used in SMP situations in order to allow code to make
188 better use of spinlocks. A spinlock, by its very nature, cannot be used
189 around code that might block. It is hoped that these capabilities will
190 make it easier to migrate the SMP master locks deeper into the kernel.
192 These routines may also be used to avoid nasty spl*() calls to get around
193 race conditions with simple conditional test/wait interlocks. You simply
196 prior to your test, then conditionally
198 only if the test fails. It is usually a good idea to cancel an
200 if you wind up never calling the related
202 but it is not required. If you do not want to waste cpu calling
204 unnecessarily, you can surround the whole thing with a second test. The
205 race condition is still handled by the inside
214 The sleep/wakeup process synchronization mechanism is very old. It
215 appeared in a very early version of Unix.
221 .Nm Asleep Ns / Ns Nm await
224 and is designed to shift the burden of blocking
225 away from extremely low level routines and push it up to their callers.
228 used to be the traditional form. It doesn't let you specify a timeout or a
230 hence it has been discontinued.
233 This man page was written by
238 were designed and written by