linux-kernel - [PATCH] irqchip/riscv-imsic: Start local sync timer on correct CPU

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Message-ID: <20250514171320.3494917-1-abrestic@rivosinc.com>
Date: Wed, 14 May 2025 10:13:20 -0700
From: Andrew Bresticker <abrestic@...osinc.com>
To: Anup Patel <anup@...infault.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Palmer Dabbelt <palmer@...belt.com>,
	Alexandre Ghiti <alex@...ti.fr>
Cc: linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Andrew Bresticker <abrestic@...osinc.com>
Subject: [PATCH] irqchip/riscv-imsic: Start local sync timer on correct CPU

When starting the local sync timer to synchronize the state of a remote
CPU it should be added on the CPU to be synchronized, not the initiating
CPU. This results in interrupt delivery being delayed until the timer
eventually runs (due to another mask/unmask/migrate operation) on the
target CPU.

Fixes: 0f67911e821c ("irqchip/riscv-imsic: Separate next and previous pointers in IMSIC vector")
Signed-off-by: Andrew Bresticker <abrestic@...osinc.com>
---
 drivers/irqchip/irq-riscv-imsic-state.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/irqchip/irq-riscv-imsic-state.c b/drivers/irqchip/irq-riscv-imsic-state.c
index bdf5cd2037f2..62f76950a113 100644
--- a/drivers/irqchip/irq-riscv-imsic-state.c
+++ b/drivers/irqchip/irq-riscv-imsic-state.c
@@ -208,17 +208,17 @@ static bool __imsic_local_sync(struct imsic_local_priv *lpriv)
 }
 
 #ifdef CONFIG_SMP
-static void __imsic_local_timer_start(struct imsic_local_priv *lpriv)
+static void __imsic_local_timer_start(struct imsic_local_priv *lpriv, unsigned int cpu)
 {
 	lockdep_assert_held(&lpriv->lock);
 
 	if (!timer_pending(&lpriv->timer)) {
 		lpriv->timer.expires = jiffies + 1;
-		add_timer_on(&lpriv->timer, smp_processor_id());
+		add_timer_on(&lpriv->timer, cpu);
 	}
 }
 #else
-static inline void __imsic_local_timer_start(struct imsic_local_priv *lpriv)
+static inline void __imsic_local_timer_start(struct imsic_local_priv *lpriv, unsigned int cpu)
 {
 }
 #endif
@@ -233,7 +233,7 @@ void imsic_local_sync_all(bool force_all)
 	if (force_all)
 		bitmap_fill(lpriv->dirty_bitmap, imsic->global.nr_ids + 1);
 	if (!__imsic_local_sync(lpriv))
-		__imsic_local_timer_start(lpriv);
+		__imsic_local_timer_start(lpriv, smp_processor_id());
 
 	raw_spin_unlock_irqrestore(&lpriv->lock, flags);
 }
@@ -278,7 +278,7 @@ static void __imsic_remote_sync(struct imsic_local_priv *lpriv, unsigned int cpu
 				return;
 		}
 
-		__imsic_local_timer_start(lpriv);
+		__imsic_local_timer_start(lpriv, cpu);
 	}
 }
 #else
-- 
2.43.0