Is it legal to initialize a linux kernel semaphore to a negative number? -


say want wake task after n separate events have occurred. legal initialize semaphore 1 - n, , down() it, wake after each of events have up()'d it?

i don't think so.

(1) semephore.count declared unsigned int. see semaphore definition:

    struct semaphore {         spinlock_t      lock;         unsigned int        count;         struct list_head    wait_list;     };

(2) down() function check count value before decrease it, make sure count not negative.

unless implement 1 mechanism, can not use semaphore directly accomplish requirement.


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