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authorEric W. Biederman <ebiederm@xmission.com>2007-01-29 15:19:05 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-01-30 11:29:58 -0500
commit8339f0008c47cdd921c73f6d53d5588b5484f93c (patch)
tree23a258422bfb3e44252ab53ab304133da20cbdc2 /arch/i386/kernel
parentc9cc8e771cb62e495765793e4b7d06016ae1b525 (diff)
[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>
Diffstat (limited to 'arch/i386/kernel')
-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 2424cc9c7b3d..6a3875f81a0a 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 }
1227 1227
1228static int __assign_irq_vector(int irq) 1228static int __assign_irq_vector(int irq)
1229{ 1229{
1230 static int current_vector = FIRST_DEVICE_VECTOR, offset = 0; 1230 static int current_vector = FIRST_DEVICE_VECTOR, current_offset = 0;
1231 int vector; 1231 int vector, offset, i;
1232 1232
1233 BUG_ON((unsigned)irq >= NR_IRQ_VECTORS); 1233 BUG_ON((unsigned)irq >= NR_IRQ_VECTORS);
1234 1234
1235 if (irq_vector[irq] > 0) 1235 if (irq_vector[irq] > 0)
1236 return irq_vector[irq]; 1236 return irq_vector[irq];
1237 1237
1238 current_vector += 8;
1239 if (current_vector == SYSCALL_VECTOR)
1240 current_vector += 8;
1241
1242 if (current_vector >= FIRST_SYSTEM_VECTOR) {
1243 offset++;
1244 if (!(offset % 8))
1245 return -ENOSPC;
1246 current_vector = FIRST_DEVICE_VECTOR + offset;
1247 }
1248
1249 vector = current_vector; 1238 vector = current_vector;
1239 offset = current_offset;
1240next:
1241 vector += 8;
1242 if (vector >= FIRST_SYSTEM_VECTOR) {
1243 offset = (offset + 1) % 8;
1244 vector = FIRST_DEVICE_VECTOR + offset;
1245 }
1246 if (vector == current_vector)
1247 return -ENOSPC;
1248 if (vector == SYSCALL_VECTOR)
1249 goto next;
1250 for (i = 0; i < NR_IRQ_VECTORS; i++)
1251 if (irq_vector[i] == vector)
1252 goto next;
1253
1254 current_vector = vector;
1255 current_offset = offset;
1250 irq_vector[irq] = vector; 1256 irq_vector[irq] = vector;
1251 1257
1252 return vector; 1258 return vector;