ARM: 9232/1: Replace this_cpu_* with raw_cpu_* in handle_bad_stack()

The hardware automatically disable the IRQ interrupt before jumping to the
interrupt or exception vector. Therefore, the preempt_disable() operation
in this_cpu_read() after macro expansion is unnecessary. In fact, function
this_cpu_read() may trigger scheduling, see pseudocode below.

Pseudocode of this_cpu_read(xx):
preempt_disable_notrace();
raw_cpu_read(xx);
if (unlikely(__preempt_count_dec_and_test()))
	__preempt_schedule_notrace();

Therefore, use raw_cpu_* instead of this_cpu_* to eliminate potential
hazards. At the very least, it reduces a few lines of assembly code.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 82fde11..a24d26e 100644 (file)
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -920,9 +920,9 @@ asmlinkage void handle_bad_stack(struct pt_regs *regs)
 {
        unsigned long tsk_stk = (unsigned long)current->stack;
 #ifdef CONFIG_IRQSTACKS
-       unsigned long irq_stk = (unsigned long)this_cpu_read(irq_stack_ptr);
+       unsigned long irq_stk = (unsigned long)raw_cpu_read(irq_stack_ptr);
 #endif
-       unsigned long ovf_stk = (unsigned long)this_cpu_read(overflow_stack_ptr);
+       unsigned long ovf_stk = (unsigned long)raw_cpu_read(overflow_stack_ptr);
 
        console_verbose();
        pr_emerg("Insufficient stack space to handle exception!");