diff options
Diffstat (limited to 'doc/user/signal.t')
| -rw-r--r-- | doc/user/signal.t | 354 |
1 files changed, 354 insertions, 0 deletions
diff --git a/doc/user/signal.t b/doc/user/signal.t new file mode 100644 index 0000000000..f6a53c1967 --- /dev/null +++ b/doc/user/signal.t @@ -0,0 +1,354 @@ +@c +@c COPYRIGHT (c) 1996. +@c On-Line Applications Research Corporation (OAR). +@c All rights reserved. +@c + +@ifinfo +@node Signal Manager, Signal Manager Introduction, EVENT_RECEIVE - Receive event condition, Top +@end ifinfo +@chapter Signal Manager +@ifinfo +@menu +* Signal Manager Introduction:: +* Signal Manager Background:: +* Signal Manager Operations:: +* Signal Manager Directives:: +@end menu +@end ifinfo + +@ifinfo +@node Signal Manager Introduction, Signal Manager Background, Signal Manager, Signal Manager +@end ifinfo +@section Introduction + +The signal manager provides the capabilities required +for asynchronous communication. The directives provided by the +signal manager are: + +@itemize @bullet +@item @code{signal_catch} - Establish an ASR +@item @code{signal_send} - Send signal set to a task +@end itemize + +@ifinfo +@node Signal Manager Background, Signal Manager Definitions, Signal Manager Introduction, Signal Manager +@end ifinfo +@section Background +@ifinfo +@menu +* Signal Manager Definitions:: +* A Comparison of ASRs and ISRs:: +* Building a Signal Set:: +* Building an ASR's Mode:: +@end menu +@end ifinfo + +@ifinfo +@node Signal Manager Definitions, A Comparison of ASRs and ISRs, Signal Manager Background, Signal Manager Background +@end ifinfo +@subsection Signal Manager Definitions + +The signal manager allows a task to optionally define +an asynchronous signal routine (ASR). An ASR is to a task what +an ISR is to an application's set of tasks. When the processor +is interrupted, the execution of an application is also +interrupted and an ISR is given control. Similarly, when a +signal is sent to a task, that task's execution path will be +"interrupted" by the ASR. Sending a signal to a task has no +effect on the receiving task's current execution state. + +A signal flag is used by a task (or ISR) to inform +another task of the occurrence of a significant situation. +Thirty-two signal flags are associated with each task. A +collection of one or more signals is referred to as a signal +set. A signal set is posted when it is directed (or sent) to a +task. A pending signal is a signal that has been sent to a task +with a valid ASR, but has not been processed by that task's ASR. + + +@ifinfo +@node A Comparison of ASRs and ISRs, Building a Signal Set, Signal Manager Definitions, Signal Manager Background +@end ifinfo +@subsection A Comparison of ASRs and ISRs + +The format of an ASR is similar to that of an ISR +with the following exceptions: + +@itemize @bullet +@item ISRs are scheduled by the processor hardware. ASRs are +scheduled by RTEMS. + +@item ISRs do not execute in the context of a task and may +invoke only a subset of directives. ASRs execute in the context +of a task and may execute any directive. + +@item When an ISR is invoked, it is passed the vector number +as its argument. When an ASR is invoked, it is passed the +signal set as its argument. + +@item An ASR has a task mode which can be different from that +of the task. An ISR does not execute as a task and, as a +result, does not have a task mode. +@end itemize + +@ifinfo +@node Building a Signal Set, Building an ASR's Mode, A Comparison of ASRs and ISRs, Signal Manager Background +@end ifinfo +@subsection Building a Signal Set + +A signal set is built by a bitwise OR of the desired +signals. The set of valid signals is SIGNAL_0 through +SIGNAL_31. If a signal is not explicitly specified in the +signal set, then it is not present. Signal values are +specifically designed to be mutually exclusive, therefore +bitwise OR and addition operations are equivalent as long as +each signal appears exactly once in the component list. + +This example demonstrates the signal parameter used +when sending the signal set consisting of SIGNAL_6, SIGNAL_15, +and SIGNAL_31. The signal parameter provided to the signal_send +directive should be SIGNAL_6 | SIGNAL_15 | SIGNAL_31. + +@ifinfo +@node Building an ASR's Mode, Signal Manager Operations, Building a Signal Set, Signal Manager Background +@end ifinfo +@subsection Building an ASR's Mode + +In general, an ASR's mode is built by a bitwise OR of +the desired mode components. The set of valid mode components +is the same as those allowed with the task_create and task_mode +directives. A complete list of mode options is provided in the +following table: + +@itemize @bullet +@item PREEMPT is masked by PREEMPT_MASK and enables preemption +@item NO_PREEMPT is masked by PREEMPT_MASK and disables preemption +@item NO_TIMESLICE is masked by TIMESLICE_MASK and disables timeslicing +@item TIMESLICE is masked by TIMESLICE_MASK and enables timeslicing +@item ASR is masked by ASR_MASK and enables ASR processing +@item NO_ASR is masked by ASR_MASK and disables ASR processing +@item INTERRUPT_LEVEL(0) is masked by INTERRUPT_MASK and enables all interrupts +@item INTERRUPT_LEVEL(n) is masked by INTERRUPT_MASK and sets interrupts level n +@end itemize + +Mode values are specifically designed to be mutually +exclusive, therefore bitwise OR and addition operations are +equivalent as long as each mode appears exactly once in the +component list. A mode component listed as a default is not +required to appear in the mode list, although it is a good +programming practice to specify default components. If all +defaults are desired, the mode DEFAULT_MODES should be specified +on this call. + +This example demonstrates the mode parameter used +with the signal_catch to establish an ASR which executes at +interrupt level three and is non-preemptible. The mode should +be set to INTERRUPT_LEVEL(3) | NO_PREEMPT to indicate the +desired processor mode and interrupt level. + +@ifinfo +@node Signal Manager Operations, Establishing an ASR, Building an ASR's Mode, Signal Manager +@end ifinfo +@section Operations +@ifinfo +@menu +* Establishing an ASR:: +* Sending a Signal Set:: +* Processing an ASR:: +@end menu +@end ifinfo + +@ifinfo +@node Establishing an ASR, Sending a Signal Set, Signal Manager Operations, Signal Manager Operations +@end ifinfo +@subsection Establishing an ASR + +The signal_catch directive establishes an ASR for the +calling task. The address of the ASR and its execution mode are +specified to this directive. The ASR's mode is distinct from +the task's mode. For example, the task may allow preemption, +while that task's ASR may have preemption disabled. Until a +task calls signal_catch the first time, its ASR is invalid, and +no signal sets can be sent to the task. + +A task may invalidate its ASR and discard all pending +signals by calling signal_catch with a value of NULL for the +ASR's address. When a task's ASR is invalid, new signal sets +sent to this task are discarded. + +A task may disable ASR processing (NO_ASR) via the +task_mode directive. When a task's ASR is disabled, the signals +sent to it are left pending to be processed later when the ASR +is enabled. + +Any directive that can be called from a task can also +be called from an ASR. A task is only allowed one active ASR. +Thus, each call to signal_catch replaces the previous one. + +Normally, signal processing is disabled for the ASR's +execution mode, but if signal processing is enabled for the ASR, +the ASR must be reentrant. + +@ifinfo +@node Sending a Signal Set, Processing an ASR, Establishing an ASR, Signal Manager Operations +@end ifinfo +@subsection Sending a Signal Set + +The signal_send directive allows both tasks and ISRs +to send signals to a target task. The target task and a set of +signals are specified to the signal_send directive. The sending +of a signal to a task has no effect on the execution state of +that task. If the task is not the currently running task, then +the signals are left pending and processed by the task's ASR the +next time the task is dispatched to run. The ASR is executed +immediately before the task is dispatched. If the currently +running task sends a signal to itself or is sent a signal from +an ISR, its ASR is immediately dispatched to run provided signal +processing is enabled. + +If an ASR with signals enabled is preempted by +another task or an ISR and a new signal set is sent, then a new +copy of the ASR will be invoked, nesting the preempted ASR. +Upon completion of processing the new signal set, control will +return to the preempted ASR. In this situation, the ASR must be +reentrant. + +Like events, identical signals sent to a task are not +queued. In other words, sending the same signal multiple times +to a task (without any intermediate signal processing occurring +for the task), has the same result as sending that signal to +that task once. + +@ifinfo +@node Processing an ASR, Signal Manager Directives, Sending a Signal Set, Signal Manager Operations +@end ifinfo +@subsection Processing an ASR + +Asynchronous signals were designed to provide the +capability to generate software interrupts. The processing of +software interrupts parallels that of hardware interrupts. As a +result, the differences between the formats of ASRs and ISRs is +limited to the meaning of the single argument passed to an ASR. +The ASR should have the following calling sequence and adhere to +C calling conventions: + +@example +rtems_asr user_routine( + rtems_signal_set signals +); +@end example + +When the ASR returns to RTEMS the mode and execution +path of the interrupted task (or ASR) is restored to the context +prior to entering the ASR. + +@ifinfo +@node Signal Manager Directives, SIGNAL_CATCH - Establish an ASR, Processing an ASR, Signal Manager +@end ifinfo +@section Directives +@ifinfo +@menu +* SIGNAL_CATCH - Establish an ASR:: +* SIGNAL_SEND - Send signal set to a task:: +@end menu +@end ifinfo + +This section details the signal manager's directives. +A subsection is dedicated to each of this manager's directives +and describes the calling sequence, related constants, usage, +and status codes. + +@page +@ifinfo +@node SIGNAL_CATCH - Establish an ASR, SIGNAL_SEND - Send signal set to a task, Signal Manager Directives, Signal Manager Directives +@end ifinfo +@subsection SIGNAL_CATCH - Establish an ASR + +@subheading CALLING SEQUENCE: + +@example +rtems_status_code rtems_signal_catch( + rtems_asr_entry asr_handler, + rtems_mode mode +); +@end example + +@subheading DIRECTIVE STATUS CODES: +@code{SUCCESSFUL} - always successful + +@subheading DESCRIPTION: + +This directive establishes an asynchronous signal +routine (ASR) for the calling task. The asr_handler parameter +specifies the entry point of the ASR. If asr_handler is NULL, +the ASR for the calling task is invalidated and all pending +signals are cleared. Any signals sent to a task with an invalid +ASR are discarded. The mode parameter specifies the execution +mode for the ASR. This execution mode supersedes the task's +execution mode while the ASR is executing. + +@subheading NOTES: + +This directive will not cause the calling task to be +preempted. + +The following task mode constants are defined by RTEMS: + +@itemize @bullet +@item PREEMPT is masked by PREEMPT_MASK and enables preemption +@item NO_PREEMPT is masked by PREEMPT_MASK and disables preemption +@item NO_TIMESLICE is masked by TIMESLICE_MASK and disables timeslicing +@item TIMESLICE is masked by TIMESLICE_MASK and enables timeslicing +@item ASR is masked by ASR_MASK and enables ASR processing +@item NO_ASR is masked by ASR_MASK and disables ASR processing +@item INTERRUPT_LEVEL(0) is masked by INTERRUPT_MASK and enables all interrupts +@item INTERRUPT_LEVEL(n) is masked by INTERRUPT_MASK and sets interrupts level n +@end itemize + +@page +@ifinfo +@node SIGNAL_SEND - Send signal set to a task, Partition Manager, SIGNAL_CATCH - Establish an ASR, Signal Manager Directives +@end ifinfo +@subsection SIGNAL_SEND - Send signal set to a task + +@subheading CALLING SEQUENCE: + +@example +rtems_status_code rtems_signal_send( + rtems_id id, + rtems_signal_set signal_set +); +@end example + +@subheading DIRECTIVE STATUS CODES: +@code{SUCCESSFUL} - signal sent successfully@* +@code{INVALID_ID} - task id invalid@* +@code{NOT_DEFINED} - ASR invalid + +@subheading DESCRIPTION: + +This directive sends a signal set to the task +specified in id. The signal_set parameter contains the signal +set to be sent to the task. + +If a caller sends a signal set to a task with an +invalid ASR, then an error code is returned to the caller. If a +caller sends a signal set to a task whose ASR is valid but +disabled, then the signal set will be caught and left pending +for the ASR to process when it is enabled. If a caller sends a +signal set to a task with an ASR that is both valid and enabled, +then the signal set is caught and the ASR will execute the next +time the task is dispatched to run. + +@subheading NOTES: + +Sending a signal set to a task has no effect on that +task's state. If a signal set is sent to a blocked task, then +the task will remain blocked and the signals will be processed +when the task becomes the running task. + +Sending a signal set to a global task which does not +reside on the local node will generate a request telling the +remote node to send the signal set to the specified task. + |