linux-kernel - [PATCH] genirq: Keep handle_nested_irq() from touching desc->threads

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Message-ID: <20240609183046.GA14050@iZj6chx1xj0e0buvshuecpZ>
Date: Mon, 10 Jun 2024 02:30:46 +0800
From: Peng Liu <iwtbavbm@...il.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: tglx@...utronix.de, gregkh@...uxfoundation.org, maz@...nel.org,
	vincent.whitchurch@...s.com, iwtbavbm@...il.com, 158710936@...com
Subject: [PATCH] genirq: Keep handle_nested_irq() from touching desc->threads_active

handle_nested_irq() is supposed to be running inside the parent thread
handler context. It per se has no dedicated kernel thread, thus shouldn't
touch desc->threads_active. The parent kernel thread has already taken
care of this.

Fixes: e2c12739ccf7 ("genirq: Prevent nested thread vs synchronize_hardirq() deadlock")
Cc: stable@...r.kernel.org
Signed-off-by: Peng Liu <iwtbavbm@...il.com>
---

Despite of its correctness, I'm afraid the testing on my only PC can't
cover the affected code path. So the patch may be totally -UNTESTED-.

 kernel/irq/chip.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index dc94e0bf2c94..85d4f29134e9 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -478,7 +478,6 @@ void handle_nested_irq(unsigned int irq)
 	}
 
 	kstat_incr_irqs_this_cpu(desc);
-	atomic_inc(&desc->threads_active);
 	raw_spin_unlock_irq(&desc->lock);
 
 	action_ret = IRQ_NONE;
@@ -487,8 +486,6 @@ void handle_nested_irq(unsigned int irq)
 
 	if (!irq_settings_no_debug(desc))
 		note_interrupt(desc, action_ret);
-
-	wake_threads_waitq(desc);
 }
 EXPORT_SYMBOL_GPL(handle_nested_irq);
 
-- 
2.39.2