[PATCH -next v5 05/22] arm64: entry: Use preempt_count() and need_resched() helper

[Jinjie Ruan <ruanjinjie@xxxxxxxxxx>]

The generic entry code uses preempt_count() and need_resched() helpers to
check if it is time to resched. Currently, arm64 use its own check logic,
that is "READ_ONCE(current_thread_info()->preempt_count == 0", which is
equivalent to "preempt_count() == 0 && need_resched()".

In preparation for moving arm64 over to the generic entry code, use
these helpers to replace arm64's own code and move it ahead.

No functional changes.

Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
---
 arch/arm64/kernel/entry-common.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index da68c089b74b..efd1a990d138 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -88,14 +88,6 @@ static inline bool arm64_need_resched(void)
        if (!need_irq_preemption())
                return false;
 
-       /*
-        * Note: thread_info::preempt_count includes both thread_info::count
-        * and thread_info::need_resched, and is not equivalent to
-        * preempt_count().
-        */
-       if (READ_ONCE(current_thread_info()->preempt_count) != 0)
-               return false;
-
        /*
         * DAIF.DA are cleared at the start of IRQ/FIQ handling, and when GIC
         * priority masking is used the GIC irqchip driver will clear DAIF.IF
@@ -141,8 +133,10 @@ static __always_inline void __exit_to_kernel_mode(struct 
pt_regs *regs,
                        return;
                }
 
-               if (arm64_need_resched())
-                       preempt_schedule_irq();
+               if (!preempt_count() && need_resched()) {
+                       if (arm64_need_resched())
+                               preempt_schedule_irq();
+               }
 
                trace_hardirqs_on();
        } else {
-- 
2.34.1