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NetBSD 6.1.5 - man page for kthread_exit (netbsd section 9)

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KTHREAD(9)			  BSD Kernel Developer's Manual 		       KTHREAD(9)

NAME
     kthread_create, kthread_destroy, kthread_exit, kthread_join -- kernel threads

SYNOPSIS
     #include <sys/kthread.h>

     int
     kthread_create(pri_t pri, int flags, struct cpu_info *ci, void (*func)(void *), void *arg,
	 lwp_t **newlp, const char *fmt, ...);

     void
     kthread_destroy(lwp_t *l);

     void
     kthread_exit(int ecode);

     int
     kthread_join(lwp_t *l);

DESCRIPTION
     Kernel threads are light-weight processes which execute entirely within the kernel.

     Any process can request the creation of a new kernel thread.  Kernel threads are not swapped
     out during memory congestion.  The VM space and limits are shared with proc0 (usually swap-
     per).

FUNCTIONS
     kthread_create(pri, flags, ci, func, arg, newlp, fmt, ...)
	      Create a kernel thread.  The arguments are as follows.

	      pri      Priority level for the thread.  If no priority level is desired specify
		       PRI_NONE, causing kthread_create() to select the default priority level.

	      flags    Flags that can be logically ORed together to alter the thread's behaviour.

	      ci       If non-NULL, the thread will be created bound to the CPU specified by ci,
		       meaning that it will only ever execute on that CPU.  By default, the
		       threads are free to execute on any CPU in the system.

	      func     A function to be called when the thread begins executing.  This function
		       must not return.  If the thread runs to completion, it must call
		       kthread_exit() to properly terminate itself.

	      arg      An argument to be passed to func().  May be NULL if not required.

	      newlp    A pointer to receive the new LWP structure for the kernel thread.  May be
		       NULL, unless KTHREAD_MUSTJOIN is specified in flags.

	      fmt      A string containing format information used to display the kernel thread
		       name.  Must not be NULL.

	      The following flags are defined.

	      KTHREAD_IDLE	Causes the thread to be created in the LSIDL (idle) state.  By
				default, the threads are created in the LSRUN (runnable) state,
				meaning they will begin execution shortly after creation.

	      KTHREAD_MPSAFE	Specifies that the thread does its own locking and so is multi-
				processor safe.  If not specified, the global kernel lock will be
				held whenever the thread is running (unless explicitly dropped by
				the thread).

	      KTHREAD_INTR	Specifies that the thread services device interrupts.  This flag
				is intended for kernel internal use and should not normally be
				specified.

	      KTHREAD_TS	Causes the kthread to be created in the SCHED_OTHER class (time-
				shared).  The thread's priority will be dynamically adjusted by
				the scheduler.	Increased activity by the kthread will cause its
				priority to fall; decreased activity will cause its priority to
				rise.  By default, kthreads are created in the SCHED_RR class,
				with a fixed priority specified by pri.  Threads in the SCHED_RR
				class do not have their priority dynamically adjusted by the
				scheduler.

	      KTHREAD_MUSTJOIN	Indicates that created kthread must be joined.	In such case
				kthread_exit() will wait until kthread_join() will be called.

     kthread_destroy(l)
	      From another thread executing in the kernel, cause a kthread to exit.  The kthread
	      must be in the LSIDL (idle) state.

     kthread_exit(ecode)
	      Exit from a kernel thread.  Must only be called by a kernel thread.

     kthread_join(l)
	      Suspend execution of calling thread until the target kthread terminates.	Conceptu-
	      ally the function can be compared to the user space pthread_join(3), however it
	      must be called only once for kernel thread which was created using the
	      KTHREAD_MUSTJOIN flag and would wait on kthread_exit.

RETURN VALUES
     Upon successful completion, kthread_create() returns 0.  Otherwise, the following error val-
     ues are returned:

     [EAGAIN]  The limit on the total number of system processes would be exceeded.

     [EAGAIN]  The limit RLIMIT_NPROC on the total number of processes under execution by this
	       user id would be exceeded.

CODE REFERENCES
     The kthread framework itself is implemented within the file sys/kern/kern_kthread.c.  Data
     structures and function prototypes for the framework are located in sys/sys/kthread.h.

SEE ALSO
     condvar(9), driver(9), softint(9), workqueue(9)

HISTORY
     The kthread framework appeared in NetBSD 1.4.

BSD					  August 7, 2011				      BSD
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