pSOSystem System Calls - Read

pSOS+ System Calls as_catch
as_catch Specifies an asynchronous signal routine (ASR).
#include
unsigned long as_catch(
void (* start_addr) (), /* ASR address */
unsigned long mode /* ASR attributes */
)
Description
Arguments
This system call allows a task to specify an asynchronous signal routine (ASR) to
handle asynchronous signals. as_catch() supplies the starting address of the
task's ASR, and its initial execution mode. If the input ASR address is zero, then the
caller is deemed to have an invalid ASR, and any signals sent to it will be rejected.
A task's ASR gains control much like an ISR. If a task has pending signals (sent via
as_send()), then the next time the task is dispatched to run, it will be forced to
first execute the task's specified ASR. A task executes its ASR according to the mode
supplied by the as_catch() call (for example, Non-preemptible, Time-slicing
enabled, etc.) Upon entry to the ASR, all pending signals — including all those
received since the last ASR invocation — are passed as an argument to the ASR. In
addition, a stack frame is built to facilitate the return from the ASR.
as_catch() replaces any previous ASR for the calling task. Therefore, a task can
have only one ASR at any time. An ASR must exit using the as_return() system
call.
start_addr Specifies the address of the ASR.
mode Specifies the ASR's attributes. mode is formed by OR-ing the
following symbolic constants (one from each pair), which are
defined in . For instance, to specify that the ASR should
have preemption turned off, you place the symbolic constant
T_NOPREEMPT in mode. To specify that the ASR should have
preemption turned off and roundrobin by time-slicing turned on,
you place both T_NOPREEMPT and T_TSLICE in mode, using the
following syntax:
T_NOPREEMPT | T_TSLICE
pSOSystem System Calls 1-3
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