genirq: Implement a sane sparse_irq allocator
The current sparse_irq allocator has several short comings due to
failures in the design or the lack of it:
- Requires iteration over the number of active irqs to find a free slot
(Some architectures have grown their own workarounds for this)
- Removal of entries is not possible
- Racy between create_irq_nr and destroy_irq (plugged by horrible
callbacks)
- Migration of active irq descriptors is not possible
- No bulk allocation of irq ranges
- Sprinkeled irq_desc references all over the place outside of kernel/irq/
(The previous chip functions series is addressing this issue)
Implement a sane allocator which fixes the above short comings (though
migration of active descriptors needs a full tree wide cleanup of the
direct and mostly unlocked access to irq_desc).
The new allocator still uses a radix_tree, but uses a bitmap for
keeping track of allocated irq numbers. That allows:
- Fast lookup of a free slot
- Allows the removal of descriptors
- Prevents the create/destroy race
- Bulk allocation of consecutive irq ranges
- Basic design is ready for migration of life descriptors after
further cleanups
The bitmap is also used in the SPARSE_IRQ=n case for lookup and
raceless (de)allocation of irq numbers. So it removes the requirement
for looping through the descriptor array to find slots.
Right now it uses sparse_irq_lock to protect the bitmap and the radix
tree, but after cleaning up all users we should be able convert that
to a mutex and to switch the radix_tree and decriptor allocations to
GFP_KERNEL.
[ Folded in a bugfix from Yinghai Lu ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 30a3009..cefacf9 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -398,6 +398,29 @@
}
#endif
+int irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node);
+void irq_free_descs(unsigned int irq, unsigned int cnt);
+
+static inline int irq_alloc_desc(int node)
+{
+ return irq_alloc_descs(-1, 0, 1, node);
+}
+
+static inline int irq_alloc_desc_at(unsigned int at, int node)
+{
+ return irq_alloc_descs(at, at, 1, node);
+}
+
+static inline int irq_alloc_desc_from(unsigned int from, int node)
+{
+ return irq_alloc_descs(-1, from, 1, node);
+}
+
+static inline void irq_free_desc(unsigned int irq)
+{
+ irq_free_descs(irq, 1);
+}
+
#endif /* CONFIG_GENERIC_HARDIRQS */
#endif /* !CONFIG_S390 */