On Wed, 2012-05-16 at 10:27 +0100, James Bottomley wrote:
> On Wed, 2012-05-16 at 08:27 +0100, James Bottomley wrote:
> > My current attempts to boot a B180 are failing on RCU:
> >
> > Initializing cgroup subsys cpuacct
> > Initializing cgroup subsys memory
> > Initializing cgroup subsys devices
> > Initializing cgroup subsys freezer
> > devtmpfs: initialized
> > NET: Registered protocol family 16
> > Backtrace:
> > [<10180fc4>] rcu_process_callbacks+0x20/0x40
> > [<101330b0>] __do_softirq+0xd8/0x190
> > [<101331d0>] run_ksoftirqd+0x68/0x118
> > [<1014a144>] kthread+0xac/0xb4
> > [<1010305c>] ret_from_kernel_thread+0x1c/0x24
> >
> >
> > Kernel Fault: Code=26 regs=2ec3c2c0 (Addr=00000000)
>
> OK, debugged this: it's a prefetch(NULL) in the RCU code. Apparently on
> the PA7300LC processor, which is what my B180 has, this is actually
> generating a dtlb insertion interruption. The fix is to nullify the
> prefetch if the address is zero, which I'm testing out now.
OK, confirmed, my B180 finally boot. This is the final patch it needed.
James
---
diff --git a/arch/parisc/include/asm/prefetch.h b/arch/parisc/include/asm/prefetch.h
index c5edc60..1ee7c82 100644
--- a/arch/parisc/include/asm/prefetch.h
+++ b/arch/parisc/include/asm/prefetch.h
@@ -21,7 +21,12 @@
#define ARCH_HAS_PREFETCH
static inline void prefetch(const void *addr)
{
- __asm__("ldw 0(%0), %%r0" : : "r" (addr));
+ __asm__(
+#ifndef CONFIG_PA20
+ /* Need to avoid prefetch of NULL on PA7300LC */
+ " extrw,u,= %0,31,32,%%r0\n"
+#endif
+ " ldw 0(%0), %%r0" : : "r" (addr));
}
/* LDD is a PA2.0 addition. */
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