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new_unrhdr, delete_unrhdr, alloc_unr, free_unr - kernel unit number allo‐

 

NAME

      new_unrhdr, delete_unrhdr, alloc_unr, free_unr - kernel unit number allo‐
      cator
 

SYNOPSIS

      #include <sys/systm.h>
 
      struct unrhdr *
      new_unrhdr(int low, int high, struct mtx *mutex);
 
      void
      delete_unrhdr(struct unrhdr *uh);
 
      int
      alloc_unr(struct unrhdr *uh);
 
      int
      alloc_unrl(struct unrhdr *uh);
 
      void
      free_unr(struct unrhdr *uh, u_int item);
 

DESCRIPTION

      The kernel unit number allocator is a generic facility, which allows to
      allocate unit numbers within a specified range.
 
      new_unrhdr(low, high, mutex)
              Initialize a new unit number allocator entity.  The low and high
              arguments specify minimum and maximum number of unit numbers.
              There is no cost associated with the range of unit numbers, so
              unless the resource really is finite, INT_MAX can be used.  If
              mutex is not NULL, it is used for locking when allocating and
              freeing units.  Otherwise, internal mutex is used.
 
      delete_unrhdr(uh)
              Destroy specified unit number allocator entity.
 
      alloc_unr(uh)
              Return a new unit number.  The lowest free number is always allo‐
              cated.  This function does not allocate memory and never sleeps,
              however it may block on a mutex.  If no free unit numbers are
              left, -1 is returned.
 
      alloc_unrl(uh)
              Same as alloc_unr() except that mutex is assumed to be already
              locked and thus is not used.
 
      free_unr(uh)
              Free a previously allocated unit number.  This function may
              require allocating memory, and thus it can sleep.  There is no
              pre-locked variant.
      The above functions are implemented in sys/kern/subr_unit.c.
 

HISTORY

      Kernel unit number allocator first appeared in FreeBSD 6.0.
 

AUTHORS

      Kernel unit number allocator was written by Poul-Henning Kamp.  This man‐
      page was written by Gleb Smirnoff.
 

Sections

Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.