uml-v2.6.12-bcrl-fix-tlb.diff

Hello all,

This patch fixes a fairly serious tlb flushing bug that makes aio use under uml very unreliable -- SEGVs, Oops and panic()s occur as a result of stale tlb entires being used by uml when aio switches mms due to the fact that uml does not implement the activate_mm() hook. This patch introduces a simple but correct approach (read: hammer) for implementing activate_mm() in uml by doing a force_flush_all() if the new mm is different from old. With this patch in place, uml is able to succeed at the aio test case that was randomly faulting for me before.

-ben

diff -purN 60_pipe_aio/include/asm-um/mmu_context.h test.diff/include/asm-um/mmu_context.h
@@ -14,8 +14,12 @@
 
 #define deactivate_mm(tsk,mm)	do { } while (0)
 
+extern void force_flush_all(void);
+
 static inline void activate_mm(struct mm_struct *old, struct mm_struct *new)
 {
+	if (old != new)
+		force_flush_all();
 }
 
 extern void switch_mm_skas(int mm_fd);