linux/lib/rcuref.c

4  * rcuref - A scalable reference count implementation for RCU managed objects
6  * rcuref is provided to replace open coded reference count implementations
8  * be visible even after the last reference has been dropped and the object
43  * rcuref uses an unsigned integer reference counter. As long as the
45  * than RCUREF_MAXREF the reference is alive:
55  * If the reference count is saturated or dead, then the increments and
56  * decrements are not harmful as the reference count still stays in the
61  * Once the last reference is dropped the reference count becomes
63  * slowpath then tries to set the reference count from RCUREF_NOREF to
65  * concurrent rcuref_get() can acquire the reference count and bring it
66  * back to RCUREF_ONEREF or even drop the reference again and mark it DEAD.
69  * DEAD + 1, which is inside the dead zone. If that happens the reference
138  * The reference count has a saturation limit RCUREF_MAXREF (INT_MAX).
139  * Once this is exceedded the reference count becomes stale by setting it
147  * All reference count increment/decrement operations are unconditional and
161  * reference count on will provide the ordering. For locked data
166  * ensures that the object is not modified when acquiring a reference
173  * If rcuref_put() successfully dropped the last reference and marked the
182  * @ref:	Pointer to the reference count
184  * Invoked when the reference count is outside of the valid zone.
187  *	False if the reference count was already marked dead
189  *	True if the reference count is saturated, which prevents the
197 	 * If the reference count was already marked dead, undo the  in rcuref_get_slowpath()
210 	 * prevents the reference count from overflowing. This leaks the  in rcuref_get_slowpath()
211 	 * object memory, but prevents the obvious reference count overflow  in rcuref_get_slowpath()
222  * @ref:	Pointer to the reference count
225  * Invoked when the reference count is outside of the valid zone.
228  *	True if this was the last reference with no future references
230  *	object, which is protected by the reference counter, for
239 	/* Did this drop the last reference? */  in rcuref_put_slowpath()
242 		 * Carefully try to set the reference count to RCUREF_DEAD.  in rcuref_put_slowpath()
262 	 * If the reference count was already in the dead zone, then this  in rcuref_put_slowpath()
263 	 * put() operation is imbalanced. Warn, put the reference count back to  in rcuref_put_slowpath()