On 01/10/2012 04:04 PM, Jan-Erik Lange wrote:
Hello, I have a question about basics of the synchronization of shared memory with mutexes. The situation: The Sender is a RT task (primary domain) and the recipient is a non-RT task (usually in the secondary domain). Namely, the receiver is used to interact with a Web server. He calls to syscalls and stuff and because of that he's usually in the secondary mode. Suppose the sender has written something to the shared memory: He uses mutex for synchronization, so he calls the rt_mutex_release() function. The receiver will now get time to work from the scheduler. He calls rt_mutex_acquire() function to lock the shared memory. Then a context switch occurs from the secondary mode in the primary mode. He has now the resource for himself. Now the scheduler lets sender-task to work and it wants to write something. So it calls rt_mutex_acquire() function. And now comes my question: Provides rt_mutex_acquire() a mechanism to signal the cheduler to immediately continue with the recipient-task? If so, how does the rt_mutex_acquire() function tells the scheduler that?
There are two tasks controlled by the same (Xenomai) scheduler. One is trying to grab a mutex the other one holds, so it is put to sleep on that mutex. The scheduler will simply switch to the next ready-to-run task since the sender task cannot run anymore, and that next task may be the receiver task. There is no special signaling magic required.
I came out because I in the documention I read the term "Rescheduling: always".
The documentation for rt_mutex_acquire is "Rescheduling: always unless the request is immediately satisfied or
timeout specifies a non-blocking operation.".
Best regards Jan _______________________________________________ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core
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