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As previously mentioned, the code in listing 9.8 is executed to make a task ready-to-run.
(4) This is a standard procedure in µC/OS-II (see section 6.02, Making a Task Ready) except for the fact that the OS_FLAG_NODE needs to be unlinked from the waiting list of the event flag group as well as the task’s OS_TCB.
The unlinking of the OS_FLAG_NODE is performed by the function OS_FlagUnlink() as shown in listing 9.9. Figure 9.5 shows the four possible locations of an OS_FLAG_NODE which needs to be removed from the event flag wait list. This is a classical doubly linked list removal problem except that there are also other pointers to adjust.
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