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Patent Absurdity

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Old 05-05-2010
Patent Absurdity
Patents are generally held to be granted on devices, or inventions.  In recent years, United States patents have been granted on processes, and even software.  "Patent Absurdity" is a half hour video outlining the dangers and difficulties surrounding the granting of software patents.  The interviews take place around the "Bilski" case appeal before the Supreme Court.  (The "Bilski" case decision is generally held to strike down software patents, but is still the subject of a good deal of debate.)

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LEARN ABOUT NETBSD

pserialize_destroy

PSERIALIZE(9)						   BSD Kernel Developer's Manual					     PSERIALIZE(9)

NAME

     pserialize -- passive serialization mechanism

SYNOPSIS

     #include <sys/pserialize.h>

     pserialize_t
     pserialize_create(void);

     void
     pserialize_destroy(pserialize_t psz);

     int
     pserialize_read_enter(void);

     void
     pserialize_read_exit(int s);

     void
     pserialize_perform(pserialize_t psz);

DESCRIPTION

     Passive serialization is a reader / writer synchronisation mechanism designed for lock-less read operations.  The read operations may happen
     from software interrupt at IPL_SOFTCLOCK.

FUNCTIONS

     pserialize_create()
	      Allocate a new synchronisation object.

     pserialize_destroy()
	      Destroy the synchronisation object.  No synchronisation activity should happen at this point.

     pserialize_read_enter()
	      Enter the critical path of the reader side.  Returns an IPL value, which must be passed to pserialize_read_exit(9).  Protected code
	      path is not allowed to block.

     pserialize_read_exit()
	      Exit the critical path of the reader side.  Takes the IPL value returned by pserialize_read_enter(9).

     pserialize_perform()
	      Perform the passive serialization on the writer side.  Passing of this function ensures that no readers are in action.  Writers must
	      be additionally serialized with a separate mechanism, e.g.  mutex(9).  Operation blocks and it may only be performed from thread
	      context.

EXAMPLES

     Typical code fragment in the writer side:

	     mutex_enter(&writer_psz_lock);
	     /*
	      * Perform the updates (e.g. remove data items from a list).
	      */
	     ...
	     pserialize_perform(object->psz);
	     /*
	      * At this point it is safe to destroy old data items.
	      */
	     mutex_exit(&writer_psz_lock);

CODE REFERENCES

     The pserialize is implemented within the file sys/kern/subr_pserialize.c.

SEE ALSO

     membar_ops(3), condvar(9), mutex(9), rwlock(9)

     Hennessy, et al., Passive serialization in a multitasking environment, US Patent and Trademark Office, US Patent 4809168, February 28, 1989.

HISTORY

     Passive serialization mechanism first appeared in NetBSD 6.0.

BSD
								   July 30, 2011							       BSD