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38 .Nm kthread_suspend_check
43 .Fn kproc_start "const void *udata"
45 .Fn kproc_shutdown "void *arg" "int howto"
47 .Fn kthread_create "void (*func)(void *)" "void *arg" "struct proc **newpp" "int flags" "int pages" "const char *fmt" "..."
49 .Fn kthread_exit "int ecode"
51 .Fn kthread_resume "struct proc *p"
53 .Fn kthread_suspend "struct proc *p" "int timo"
55 .Fn kthread_suspend_check "struct proc *p"
61 daemons such as bufdaemon, pagedaemon, vmdaemon, and the syncer and is intended
66 argument is actually a pointer to a
68 which describes the kernel thread that should be created:
69 .Bd -literal -offset indent
73 struct proc **global_procpp;
77 The structure members are used by
80 .Bl -tag -width "global_procpp" -offset indent
82 String to be used for the name of the process.
83 This string will be copied into the
85 member of the new process'
88 The main function for this kernel process to run.
92 pointer that should be updated to point to the newly created process' process
101 function is used to create a kernel thread.
102 The new thread shares its address space with process 0, the swapper process,
103 and runs in kernel mode only.
106 argument specifies the function that the thread should execute.
109 argument is an arbitrary pointer that is passed in as the only argument to
111 when it is called by the new process.
116 pointer that is to be updated to point to the newly created process.
122 argument specifies a set of flags as described in
126 argument specifies the size of the new kernel thread's stack in pages.
127 If 0 is used, the default kernel stack size is allocated.
128 The rest of the arguments form a
130 argument list that is used to build the name of the new thread and is stored
133 member of the new thread's
138 function is used to terminate kernel threads.
139 It should be called by the main function of the kernel thread rather than
140 letting the main function return to its caller.
143 argument specifies the exit status of the thread.
147 .Fn kthread_suspend ,
149 .Fn kthread_suspend_check
150 functions are used to suspend and resume a kernel thread.
151 During the main loop of its execution, a kernel thread that wishes to allow
152 itself to be suspended should call
153 .Fn kthread_suspend_check
156 as the only argument.
157 This function checks to see if the kernel thread has been asked to suspend.
160 until it is told to resume.
161 Once it has been told to resume it will return allowing execution of the
162 kernel thread to continue.
163 The other two functions are used to notify a kernel thread of a suspend or
167 argument points to the
169 of the kernel thread to suspend or resume.
171 .Fn kthread_suspend ,
174 argument specifies a timeout to wait for the kernel thread to acknowledge the
175 suspend request and suspend itself.
179 function is meant to be registered as a shutdown event for kernel threads that
180 need to be suspended voluntarily during system shutdown so as not to interfere
181 with system shutdown activities.
182 The actual suspension of the kernel thread is done with
183 .Fn kthread_suspend .
190 functions return zero on success and non-zero on failure.
192 This example demonstrates the use of a
193 .Li struct kproc_desc
198 .Fn kthread_suspend_check
202 .Bd -literal -offset indent
203 static struct proc *bufdaemonproc;
205 static struct kproc_desc buf_kp = {
210 SYSINIT(bufdaemon, SI_SUB_KTHREAD_BUF, SI_ORDER_FIRST, kproc_start,
218 * This process needs to be suspended prior to shutdown sync.
220 EVENTHANDLER_REGISTER(shutdown_pre_sync, kproc_shutdown,
221 bufdaemonproc, SHUTDOWN_PRI_LAST);
224 kthread_suspend_check(bufdaemonproc);
234 functions will fail if:
239 argument does not reference a kernel thread.
244 function will fail if:
247 The system-imposed limit on the total
248 number of processes under execution would be exceeded.
249 The limit is given by the
256 flag was specified in the
266 function first appeared in
273 .Fn kthread_suspend ,
275 .Fn kthread_suspend_check
276 functions were introduced in
283 .Fn kthread_suspend ,
285 .Fn kthread_suspend_check
291 .Fn kproc_suspend_loop ,