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Subjecti386 doublefault handler is broken with CONFIG_DEBUG_SPINLOCK
The new percpu code has apparently broken the doublefault handler
when CONFIG_DEBUG_SPINLOCK is set. Doublefault is handled by
a hardware task, making the check

SPIN_BUG_ON(lock->owner == current, lock, "recursion");

fault because it uses the FS register to access the percpu data
for current, and that register is zero in the new TSS. (The trace
I saw was on 2.6.20 where it was GS, but it looks like this will
still happen with FS on 2.6.22.)

Initializing FS in the doublefault_tss should fix it.

Signed-off-by: Chuck Ebbert <cebbert@redhat.com>

---
NOTE: not even compile tested.

arch/i386/kernel/doublefault.c | 1 +
1 file changed, 1 insertion(+)
--- linux-2.6.22.noarch.orig/arch/i386/kernel/doublefault.c
+++ linux-2.6.22.noarch/arch/i386/kernel/doublefault.c
@@ -63,6 +63,7 @@ struct tss_struct doublefault_tss __cach
.cs = __KERNEL_CS,
.ss = __KERNEL_DS,
.ds = __USER_DS,
+ .fs = __KERNEL_PERCPU,

.__cr3 = __pa(swapper_pg_dir)
}
-
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