sparc64: Adjust __raw_local_irq_save() to cooperate in NMIs.

[ Upstream commits 0c25e9e6cbe7b233bb91d14d0e2c258bf8e6ec83 and
   c011f80ba0912486fe51dd2b3f71d9b33a151188 ]

If we are in an NMI then doing a plain raw_local_irq_disable() will
write PIL_NORMAL_MAX into %pil, which is lower than PIL_NMI, and thus
we'll re-enable NMIs and recurse.

Doing a simple:

	%pil = %pil | PIL_NORMAL_MAX

does what we want, if we're already at PIL_NMI (15) we leave it at
that setting, else we set it to PIL_NORMAL_MAX (14).

This should get the function tracer working on sparc64.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 20 insertions, 3 deletions

diff --git a/arch/sparc/include/asm/irqflags_64.h b/arch/sparc/include/asm/irqflags_64.h
index 8b49bf920df3..bfa1ea45b4cd 100644
--- a/arch/sparc/include/asm/irqflags_64.h
+++ b/arch/sparc/include/asm/irqflags_64.h
@@ -76,9 +76,26 @@ static inline int raw_irqs_disabled(void)
  */
 static inline unsigned long __raw_local_irq_save(void)
 {
-        unsigned long flags = __raw_local_save_flags();
-
-        raw_local_irq_disable();
+        unsigned long flags, tmp;
+
+        /* Disable interrupts to PIL_NORMAL_MAX unless we already
+         * are using PIL_NMI, in which case PIL_NMI is retained.
+         *
+         * The only values we ever program into the %pil are 0,
+         * PIL_NORMAL_MAX and PIL_NMI.
+         *
+         * Since PIL_NMI is the largest %pil value and all bits are
+         * set in it (0xf), it doesn't matter what PIL_NORMAL_MAX
+         * actually is.
+         */
+        __asm__ __volatile__(
+                "rdpr   %%pil, %0\n\t"
+                "or     %0, %2, %1\n\t"
+                "wrpr   %1, 0x0, %%pil"
+                : "=r" (flags), "=r" (tmp)
+                : "i" (PIL_NORMAL_MAX)
+                : "memory"
+        );
 
         return flags;
 }