linux-kernel - [PATCH -next v5 05/22] arm64: entry: Use preempt_count() and need

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Message-ID: <20241206101744.4161990-6-ruanjinjie@huawei.com>
Date: Fri, 6 Dec 2024 18:17:27 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: <catalin.marinas@....com>, <will@...nel.org>, <oleg@...hat.com>,
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Subject: [PATCH -next v5 05/22] arm64: entry: Use preempt_count() and need_resched() helper

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@...wei.com>
---
 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