arch/tile: Various cleanups.

This change rolls up random cleanups not representing any actual bugs.

- Remove a stale CONFIG_ value from the default tile_defconfig
- Remove unused tns_atomic_xxx() family of methods from <asm/atomic.h>
- Optimize get_order() using Tile's "clz" instruction
- Fix a bad hypervisor upcall name (not currently used in Linux anyway)
- Use __copy_in_user_inatomic() name for consistency, and export it
- Export some additional hypervisor driver I/O upcalls and some homecache calls
- Remove the obfuscating MEMCPY_TEST_WH64 support code
- Other stray comment cleanups, #if 0 removal, etc.

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

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
index 0011f06b4fe2..704f3e8a4385 100644
--- a/arch/tile/mm/fault.c
+++ b/arch/tile/mm/fault.c
@@ -567,6 +567,14 @@ do_sigbus:
  * since that might indicate we have not yet squirreled the SPR
  * contents away and can thus safely take a recursive interrupt.
  * Accordingly, the hypervisor passes us the PC via SYSTEM_SAVE_1_2.
+ *
+ * Note that this routine is called before homecache_tlb_defer_enter(),
+ * which means that we can properly unlock any atomics that might
+ * be used there (good), but also means we must be very sensitive
+ * to not touch any data structures that might be located in memory
+ * that could migrate, as we could be entering the kernel on a dataplane
+ * cpu that has been deferring kernel TLB updates.  This means, for
+ * example, that we can't migrate init_mm or its pgd.
  */
 struct intvec_state do_page_fault_ics(struct pt_regs *regs, int fault_num,
 				      unsigned long address,