CooCox CoOS User's Guide

Code 3 The use of the mutex section
void myTaskA(void* pdata)
{
mutexID = CoCreateMutex();
CoEnterMutexSection(mutexID ); // enter the mutex section
........... // critical codes
CoLeaveMutexSection(mutexID ); // leave the mutex section
}
void myTaskB(void* pdata)
{
CoEnterMutexSection(mutexID ); // enter the mutex section
........... // critical codes
CoLeaveMutexSection(mutexID ); // leave the mutex section
}
5.1.3 Flags
When a task wants to synchronize with a number of events, flags are
needed. If the task synchronizes with a single event, it can be called
independent synchronization (logical OR relationship). If it synchronizes with a
number of events, then called associated synchronization (logical AND
relationship).
CooCox CoOS supports 32 flags to the maximum at the same time. It
supports that multiple tasks waiting for a single event or multiple events. When
the flags that the waiting tasks waiting for are in the not-ready state, these
tasks can not be scheduled. However, once the flags turn to the ready state,
they will be resumed soon.
According to the types of the flags, the side effects are different when the
tasks have waited for the flags successfully. There are two kinds of flags in
CooCox CoOS: the ones reset manually and the ones reset automatically. When
a task has waited for a flag which reset automatically, the system will convert
the flag to not-ready state. On the contrary, if the flag is reset manually, there
won’t be any side effect. Therefore, when a flag which reset manually converts
to the ready state, all the tasks which waiting for this event will convert to the
ready state as far as you call CoClearFlag() to reset the flag to the not-ready
state. When a flag which reset automatically converts to the ready state, only
one task which waiting for this event will convert to the ready state. Since the
waiting list of the event flags is ordered by the principle of FIFO, towards the
event which reset automatically only the first task of the waiting list converts to
the ready state and others that waiting for this flag are still in the waiting state.
Suppose there are three tasks (A, B, C) waiting for the same flag I which
reset manually. When I is ready, all the tasks will be converted (A, B, C) to the
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