The process and exception management kernel services provided by the base kernel provide the capability to:
Kernel extensions use the creatp and initp kernel services to create and intialize a kernel process. The setpinit kernel service allow a kernel process to change its parent process from the one that created it to the init process, so that the creating process does not receive the death-of-child process signal upon kernel process termination. "Using Kernel Processes supplies additional information concerning use of these services.
Kernel extensions use the thread_create and kthread_start services to create and initialize kernel-only threads. "Understanding Kernel Threads provides more information about threads.
The thread_setsched service is used to control the scheduling parameters, priority and scheduling policy, of a thread.
The getpid kernel service is used by a kernel extension in either the process or interrupt environment to determine the current execution environment and obtain the process ID of the current process if in the process environment. The rusage_incr service provides an access to the rusage structure.
The thread-specific uthread structure is also encapsulated. The getuerror and setuerror kernel services should be used to access the ut_error field. The thread_self kernel service should be used to get the current thread's ID.
The setjmpx, clrjmpx, and longjmpx kernel services allow a kernel extension to register an exception handler by:
Refer to "Handling Exceptions While in a System Call" for additional information concerning use of these services.
Signals can be posted either to a kernel process or to a kernel thread. The pidsig service posts a signal to a specified kernel process; the kthread_kill service posts a signal to a specified kernel thread. A thread uses the sig_chk service to poll for signals delivered to the kernel process or thread in the kernel mode.
"Kernel Process Signal and Exception Handling provides more information about signal management.
The event notification services provide support for two types of interprocess communications:
|Primitive||Allows only one process thread waiting on the event.|
|Shared||Allows multiple processes threads waiting on the event.|
The et_wait and et_post kernel services support single waiter event notification by using mutually agreed upon event control bits for the kernel thread being posted. There are a limited number of control bits available for use by kernel extensions. If the kernel_lock is owned by the caller of the et_wait service, it is released and acquired again upon wakeup.
The following kernel services support a shared event notification mechanism that allows for multiple threads to be waiting on the shared event.
These services support an unlimited number of shared events (by using caller-supplied event words). The following list indicates methods to wait for an event to occur:
The e_clear_wait service can be used by a thread or an interrupt handler to wake up a specified thread, or by a thread that called e_assert_wait to remove itself from the event queue without blocking when calling e_block_thread. The other wakeup services are event-based. The e_wakeup and e_wakeup_w_result services wake up every thread sleeping on an event queue; while the e_wakeup_one service wakes up only the most favored thread. The e_wakeup_w_sig service posts a signal to every thread sleeping on an event queue, waking up all the threads whose sleep is interruptible.
The e_sleep and e_sleepl kernel services are provided for code that was written for previous releases of the operating system. Threads which have called one of these services are woken up by the e_wakeup, e_wakeup_one, e_wakeup_w_result, e_wakeup_w_sig, or e_clear_wait kernel services. If the caller of the e_sleep service owns the kernel lock, it is released before waiting and is acquired again upon wakeup. The e_sleepl service provides the same function as the e_sleep service except that a caller-specified lock is released and acquired again instead of the kernel_lock.
The Process, Thread, and Exception Management kernel services are listed below.
|clrjmpx||Removes a saved context by popping the most recently saved jump buffer from the list of saved contexts.|
|creatp||Creates a new kernel process.|
|e_assert_wait||Asserts that the calling kernel thread is going to sleep.|
|e_block_thread||Blocks the calling kernel thread.|
|e_clear_wait||Clears the wait condition for a kernel thread.|
|e_sleep, e_sleep_thread, or e_sleepl||Forces the calling kernel thread to wait for the occurrence of a shared event.|
|e_sleep_thread||Forces the calling kernel thread to wait the occurrence of a shared event.|
|e_wakeup, e_wakeup_one, or e_wakeup_w_result||Notifies kernel threads waiting on a shared event of the event's occurrence.|
|e_wakeup_w_sig||Posts a signal to sleeping kernel threads.|
|et_post||Notifies a kernel thread of the occurrence of one or more events.|
|et_wait||Forces the calling kernel thread to wait for the occurrence of an event.|
|getpid||Gets the process ID of the current process.|
|getppidx||Gets the parent process ID of the specified process.|
|initp||Changes the state of a kernel process from idle to ready.|
|kthread_kill||Posts a signal to a specified kernel-only thread.|
|kthread_start||Starts a previously created kernel-only thread.|
|limit_sigs||Changes the signal mask for the calling kernel thread.|
|longjmpx||Allows exception handling by causing execution to resume at the most recently saved context.|
|NLuprintf||Submits a request to print an internationalized message to the controlling terminal of a process.|
|pgsignal||Sends a signal to a process group.|
|pidsig||Sends a signal to a process.|
|rusage_incr||Increments a field of the rusage structure.|
|setjmpx||Allows saving the current execution state or context.|
|setpinit||Sets the parent of the current kernel process to the init process.|
|sig_chk||Provides the calling kernel thread with the ability to poll for receipt of signals.|
|sigsetmask||Changes the signal mask for the calling kernel thread.|
|sleep||Forces the calling kernel thread to wait on a specified channel.|
|thread_create||Creates a new kernel-only thread in the calling process.|
|thread_self||Returns the caller's kernel thread ID.|
|thread_setsched||Sets kernel thread scheduling parameters.|
|thread_terminate||Terminates the calling kernel thread.|
|uprintf||Submits a request to print a message to the controlling terminal of a process.|
Understanding Execution Environments.
Understanding Exception Handling.