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authorEric W. Biederman <ebiederm@xmission.com>2007-01-29 13:19:05 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-01-30 08:29:58 -0800
commit8339f0008c47cdd921c73f6d53d5588b5484f93c (patch)
tree23a258422bfb3e44252ab53ab304133da20cbdc2
parentc9cc8e771cb62e495765793e4b7d06016ae1b525 (diff)
downloadlinux-2.6.34-ux500-8339f0008c47cdd921c73f6d53d5588b5484f93c.tar.gz
[PATCH] i386: In assign_irq_vector look at all vectors before giving up
When the world was a simple and static place setting up irqs was easy. It sufficed to allocate a linux irq number and a find a free cpu vector we could receive that linux irq on. In those days it was a safe assumption that any allocated vector was actually in use so after one global pass through all of the vectors we would have none left. These days things are much more dynamic with interrupt controllers (in the form of MSI or MSI-X) appearing on plug in cards and linux irqs appearing and disappearing. As these irqs come and go vectors are allocated and freed, invalidating the ancient assumption that all allocated vectors stayed in use forever. So this patch modifies the vector allocator to walk through every possible vector before giving up, and to check to see if a vector is in use before assigning it. With these changes we stop leaking freed vectors and it becomes possible to allocate and free irq vectors all day long. This changed was modeled after the vector allocator on x86_64 where this limitation has already been removed. In essence we don't update the static variables that hold the position of the last vector we allocated until have successfully allocated another vector. This allows us to detect if we have completed one complete scan through all of the possible vectors. Acked-by: Auke Kok <auke-jan.h.kok@intel.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/i386/kernel/io_apic.c32
1 files changed, 19 insertions, 13 deletions
diff --git a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c
index 2424cc9c7b3..6a3875f81a0 100644
--- a/arch/i386/kernel/io_apic.c
+++ b/arch/i386/kernel/io_apic.c
@@ -1227,26 +1227,32 @@ static u8 irq_vector[NR_IRQ_VECTORS] __read_mostly = { FIRST_DEVICE_VECTOR , 0 }
static int __assign_irq_vector(int irq)
{
- static int current_vector = FIRST_DEVICE_VECTOR, offset = 0;
- int vector;
+ static int current_vector = FIRST_DEVICE_VECTOR, current_offset = 0;
+ int vector, offset, i;
BUG_ON((unsigned)irq >= NR_IRQ_VECTORS);
if (irq_vector[irq] > 0)
return irq_vector[irq];
- current_vector += 8;
- if (current_vector == SYSCALL_VECTOR)
- current_vector += 8;
-
- if (current_vector >= FIRST_SYSTEM_VECTOR) {
- offset++;
- if (!(offset % 8))
- return -ENOSPC;
- current_vector = FIRST_DEVICE_VECTOR + offset;
- }
-
vector = current_vector;
+ offset = current_offset;
+next:
+ vector += 8;
+ if (vector >= FIRST_SYSTEM_VECTOR) {
+ offset = (offset + 1) % 8;
+ vector = FIRST_DEVICE_VECTOR + offset;
+ }
+ if (vector == current_vector)
+ return -ENOSPC;
+ if (vector == SYSCALL_VECTOR)
+ goto next;
+ for (i = 0; i < NR_IRQ_VECTORS; i++)
+ if (irq_vector[i] == vector)
+ goto next;
+
+ current_vector = vector;
+ current_offset = offset;
irq_vector[irq] = vector;
return vector;