Comments on: semophore doubt https://www.emblogic.com/blog/05/semophore-doubt/ Embedded System and ARM Training Mon, 07 Oct 2013 04:00:03 +0000 hourly 1 http://wordpress.org/?v=3.9.1 By: Vaibhav Singh https://www.emblogic.com/blog/05/semophore-doubt/#comment-747 Mon, 07 May 2012 10:23:27 +0000 http://emblogic.org/blog/?p=2667#comment-747 If you check the kernel Sources the semaphore structure contains only three members 1-Spinlock 2-unsigned int count 3-struct list_head *list_head;

There is a comment above this structure that you cannot access the members of this structure directly .

And the value u give as second argument of sema_init() is jst decide the maximum length of the list_head type link list . So the value (2nd argument of sema_init()) does not define the processes which can access the critical section . The value defines the maximum no. of processes that are maintained by that structure . It also includes the spinlock locking mechenism. And this is the main reason tht semaphore is a heavyweight synchronisation technique .

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