MIPS: Init new mmu_context for each possible CPU to avoid memory corruption

Currently, init_new_context() only for each online CPU, this may cause
memory corruption when CPU hotplug and fork() happens at the same time.
To avoid this, we make init_new_context() cover each possible CPU.

Scenario:
1, CPU#1 is being offline;
2, On CPU#0, do_fork() call dup_mm() and copy a mm_struct to the child;
3, On CPU#0, dup_mm() call init_new_context(), since CPU#1 is offline
   and init_new_context() only covers the online CPUs, child has the
   same asid as its parent on CPU#1 (however, child's asid should be 0);
4, CPU#1 is being online;
5, Now, if both parent and child run on CPU#1, memory corruption (e.g.
   segfault, bus error, etc.) will occur.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Acked-by: David Daney <david.daney@cavium.com>
Patchwork: http://patchwork.linux-mips.org/patch/4995/
Acked-by: John Crispin <blogic@openwrt.org>

diff --git a/arch/mips/include/asm/mmu_context.h b/arch/mips/include/asm/mmu_context.h
index e81d719..49d220c 100644 (file)
--- a/arch/mips/include/asm/mmu_context.h
+++ b/arch/mips/include/asm/mmu_context.h
@@ -133,7 +133,7 @@ init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 {
        int i;
 
-       for_each_online_cpu(i)
+       for_each_possible_cpu(i)
                cpu_context(i, mm) = 0;
 
        return 0;