Hi... > > I have just checked mailing list archive to make sure whether I have > send out the message body correctly, and yes, it's there. So it must > be my poor English which makes you can't understand my question, I > feel lose, really. :-( I felt obligated to reply. Do you mind? :) > Anyhow, thanks for your kindly reply, and let me try it again. There > are 3 questions about kernel 2.4: > > 1. According to "Linux device driver, 2e", Chapter 6 Flow of Time, > Kernel Timers, it says: > > " If the timer function can restart the timer itself (a common > pattern), you should also have a "stop timer'' flag that you set > before calling del_timer_sync. The timer function should then check > that flag and not reschedule itself with add_timer if the flag has > been set." > > My question is: why should we have a "stop timer" flag here? Is there > any problem without the flag? Not sure, but if you want to re-arm the timer, you should use mod_timer()/mod_timer_sync() instead IIRC. The later is preferred in SMP.. It has something to do with atomicity/reentrancy, but can't remember. > The previous quoted text can be found online here: > http://www.xml.com/ldd/chapter/book/ch06.html#t5 > > 2. Say we have a "struct tq_struct my_task;", my question is: is there > any way to indicate the status of my_task? Is it running? Is it in the > task queue waiting for running? Or is it neither in the task queue nor > running? one thing for sure, if it's in the list...it is waiting for running. If it's not in linked list (i forgot which one): 1. it isn't queued yet or 2. it's already running how about settting a flag? anything....simply a global variable maybe....when it hit the function, set it let's say "1". When it's about to leave, set it to "2". Comments? > 3. Suppose my_task is created in a kernel module "foobar", and when we > "rmmod foobar", we find that my_task is running, so we must waiting > for its completion. A common way to do this is calling > interruptible_sleep_on() in module_exit(), and let my_task.routine() > to wake up it like this: > > void my_task_routine(void *dummy) > { > ..... > ..... > wake_up_interruptible(...); > } > > Well, as we know, function have its prolog and epilog. After > wake_up_interruptible(), the rmmod thread executes and frees the > memory of this module. At this time, memory containing epilog of the > my_task_routine() was freed, it may oops when those "epilog" execute > later on. > > My last question is: is this a trap? Or do I make some mistakes? In your module_exit, make it check a flag. This flag is set by your my_task_routine, let's say "2" means "i will quite". When this flag != 2, do schedule(). repeat doing this in module_exit until it hits "2". At least, this is my idea to offer. regards, Mulyadi. -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
