Hi Daniel, I wanted to implement it as part of an assignment. Anyways, I back off my last statement that there is no functionality to do a selective wake up. I could find a function called wake_up_process that takes a task_struct pointer and wakes up the corresponding process. All I am doing in my system call is just tracking which thread is calling on which character ( pseudo - semaphore) and which thread needs to be woke up.
Functions that I am using - wait_event_interruptible () - to put a process / thread to sleep and also a condition which when made true, the slept process is woke up. wake_up_process() - when passed a pointer of struct task_struct type wakes up that particular process. I would share the code once my assignment's deadline is over. I think it is currently very limited to number of pseudo semaphores and not quite general. Thanks for your comment. Regards, Onkar Deshpande On Fri, May 1, 2009 at 2:31 AM, Daniel Baluta <[email protected]>wrote: > On Fri, May 1, 2009 at 6:44 AM, Onkar Deshpande > <[email protected]> wrote: > > Hi, > > > > I am writing a system call which is called as rendezvous_wait(). This > system > > call is passed a character which would act as a kind of identifier. My > > application program will create threads and each thread will call > > rendezvous_wait with a character. Consider thread1 calls the system call > > passing x. Since it is the first one to call that system with parameter > x, > > thread1 will be pushed on a wait list. i.e. kernel should force it to > sleep. > > Whenever any other thread calls rendezvous_wait() with same parameter x, > > thread1 should be taken out from the wait queue and put on the run queue, > > which could later be scheduled by the scheduler. This system call is > called > > as rendezvous_wait because it is much similar to meeting where one person > > waits for other and when other comes, they both live for some another > > location. > > Hi, > Have you considered using condition variables? ([1]). > Why do you need a new system call? > > thanks, > Daniel. > > [1]https://computing.llnl.gov/tutorials/pthreads/#ConditionVariables >
