[PATCH] ppc32: fix destroy_context() race condition
Fix for a race condition when a task gets preempted by another task while
executing the destroy_context(...) in a FEW_CONTEXTS environment.
mm->context == NO_CONTEXT but the context_map may indicate all contexts are
in use.
The solution to this problem is to disable kernel preemption while
destroying a MMU context.
Signed-off-by: Guillaume Autran <gautran@mrv.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/asm-ppc/mmu_context.h b/include/asm-ppc/mmu_context.h
index ccabbce..afe26ff 100644
--- a/include/asm-ppc/mmu_context.h
+++ b/include/asm-ppc/mmu_context.h
@@ -149,6 +149,7 @@
*/
static inline void destroy_context(struct mm_struct *mm)
{
+ preempt_disable();
if (mm->context != NO_CONTEXT) {
clear_bit(mm->context, context_map);
mm->context = NO_CONTEXT;
@@ -156,6 +157,7 @@
atomic_inc(&nr_free_contexts);
#endif
}
+ preempt_enable();
}
static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
