arch/tile: use interrupt critical sections less

In general we want to avoid ever touching memory while within an
interrupt critical section, since the page fault path goes through
a different path from the hypervisor when in an interrupt critical
section, and we carefully decided with tilegx that we didn't need
to support this path in the kernel.  (On tilepro we did implement
that path as part of supporting atomic instructions in software.)

In practice we always need to touch the kernel stack, since that's
where we store the interrupt state before releasing the critical
section, but this change cleans up a few things.  The IRQ_ENABLE
macro is split up so that when we want to enable interrupts in a
deferred way (e.g. for cpu_idle or for interrupt return) we can
read the per-cpu enable mask before entering the critical section.
The cache-migration code is changed to use interrupt masking instead
of interrupt critical sections.  And, the interrupt-entry code is
changed so that we defer loading "tp" from per-cpu data until after
we have released the interrupt critical section.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/tile/kernel/entry.S b/arch/tile/kernel/entry.S
index ec91568df880..133c4b56a99e 100644
--- a/arch/tile/kernel/entry.S
+++ b/arch/tile/kernel/entry.S
@@ -100,8 +100,9 @@ STD_ENTRY(smp_nap)
  */
 STD_ENTRY(_cpu_idle)
         movei r1, 1
+        IRQ_ENABLE_LOAD(r2, r3)
         mtspr INTERRUPT_CRITICAL_SECTION, r1
-        IRQ_ENABLE(r2, r3)             /* unmask, but still with ICS set */
+        IRQ_ENABLE_APPLY(r2, r3)       /* unmask, but still with ICS set */
         mtspr INTERRUPT_CRITICAL_SECTION, zero
         .global _cpu_idle_nap
 _cpu_idle_nap: