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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 $
43 .Fn tsleep "void *ident" "int priority" "const char *wmesg" "int timo"
45 .Fn asleep "void *ident" "int priority" "const char *wmesg" "int timo"
47 .Fn await "int priority" "int timo"
49 .Fn wakeup "void *ident"
51 .Fn wakeup_one "void *ident"
57 handle event-based process blocking. If a process must wait for an
58 external event, it is put on sleep by
62 is an arbitrary address that uniquely identifies the event on which
63 the process is being asleep. All processes sleeping on a single
67 often called from inside an interrupt routine, to indicate that the
68 resource the process was blocking on is available now.
72 is a string describing the sleep condition for tools like
74 Due to the limited space of those programs to display arbitrary strings,
75 this message should not be longer than 6 characters.
79 function is used to make the first process in the queue that is
80 sleeping on the parameter
82 runnable. This can prevent the system from becoming saturated
83 when a large number of processes are sleeping on the same address,
84 but only one of them can actually do any useful work when made
88 is the general sleep call. Suspends the current process until a wakeup is
89 performed on the specified identifier. The process will then be made
90 runnable with the specified
94 \&/ hz seconds (0 means no timeout). If
98 flag, signals are checked before and after sleeping, else signals are
99 not checked. Returns 0 if awakened,
101 if the timeout expires. If
103 is set and a signal needs to be delivered,
105 is returned if the current system call should be restarted if
108 is returned if the system call should be interrupted by the signal
113 implements the new asynchronous sleep function. It takes the same arguments
116 and places the process on the appropriate wait queue, but
118 leaves the process runnable and returns immediately. The caller is then
119 expected to, at some point in the future, call
121 to actually wait for the previously queued wait condition.
124 is called several times, only the most recent call is effective.
126 may be called with an
129 to remove any previously queued condition.
132 implements the new asynchronous wait function. When
134 is called on an identifier it associates the process with that
135 identifier but does not block.
137 will actually block the process until
139 is called on that identifier any time after the
149 call is effectively a NOP.
152 is called multiple times without an intervening
156 is effectively a NOP but will also call
160 function allows you to override the priority and timeout values to be used.
161 If the value -1 is specified for an argument, the value is taken from the
164 call. If -1 is passed for the priority you must be prepared to catch signal
165 conditions if the prior call to
167 specified it in its priority. If -1 is passed for the timeout you must be
168 prepared to catch a timeout condition if the prior call to
170 specified a timeout. When you use -1, it is usually a good idea to not make
171 assumptions as to the arguments used by the prior
179 functions are mainly used by the kernel to shift the burden of blocking
180 away from extremely low level routines and to push it onto their callers.
181 This in turn allows more complex interlocking code to
183 of a temporary resource failure
184 (such as lack of memory) in order to release major locks prior to actually
185 blocking, and to then retry the operation on wakeup. This key feature is
186 expected to be heavily used in SMP situations in order to allow code to make
187 better use of spinlocks. A spinlock, by its very nature, cannot be used
188 around code that might block. It is hoped that these capabilities will
189 make it easier to migrate the SMP master locks deeper into the kernel.
191 These routines may also be used to avoid nasty spl*() calls to get around
192 race conditions with simple conditional test/wait interlocks. You simply
195 prior to your test, then conditionally
197 only if the test fails. It is usually a good idea to cancel an
199 if you wind up never calling the related
201 but it is not required. If you do not want to waste cpu calling
203 unnecessarily, you can surround the whole thing with a second test. The
204 race condition is still handled by the inside
213 The sleep/wakeup process synchronization mechanism is very old. It
214 appeared in a very early version of Unix.
220 .Nm Asleep Ns / Ns Nm await
223 and is designed to shift the burden of blocking
224 away from extremely low level routines and push it up to their callers.
227 used to be the traditional form. It doesn't let you specify a timeout or a
229 hence it has been discontinued.
232 This man page was written by
237 were designed and written by