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Subject[PATCH 2/2] ARM: Replace this_cpu_* with raw_cpu_* in panic_bad_stack()
Date
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>
---
KernelVersion: v6.0-rc2
arch/arm/kernel/traps.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 1518a1f443ff866..d5903d790cf3b7e 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -927,9 +927,9 @@ 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!");
--
2.25.1
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