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Message-Id: <20220427060338.7276-1-kernelfans@gmail.com>
Date: Wed, 27 Apr 2022 14:03:38 +0800
From: Pingfan Liu <kernelfans@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Pingfan Liu <kernelfans@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
"Rafael J. Wysocki" <rafael@...nel.org>
Subject: [PATCHv2] genirq/PM: Make for_each_irq_desc() safe of irq_desc release
First, this is a suspicion of the code, not a really encountered bug.
*** The scenario ***
Two threads involved
threadA "hibernate" runs suspend_device_irqs()
threadB "rcu_cpu_kthread" runs rcu_core()->rcu_do_batch(), which releases
object, let's say irq_desc
Zoom in:
threadA threadB
for_each_irq_desc(irq, desc) {
get irq_descA which is under freeing
--->preempted by rcu_core()->rcu_do_batch() which releases irq_descA
raw_spin_lock_irqsave(&desc->lock, flags);
//Oops
And since in the involved code piece, suspend_device_irqs() runs in a
preemptible context, and there may be more than one thread at this
point. So the preemption can happen.
*** The fix ***
Since there is a blockable synchronize_irq() inside the code piece,
resorting to irq_lock_sparse() to protect the irq_desc from
disappearing.
Signed-off-by: Pingfan Liu <kernelfans@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
To: linux-kernel@...r.kernel.org
---
v1 -> v2: improve commit log
kernel/irq/pm.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c
index ca71123a6130..4b67a4c7de3c 100644
--- a/kernel/irq/pm.c
+++ b/kernel/irq/pm.c
@@ -133,6 +133,7 @@ void suspend_device_irqs(void)
struct irq_desc *desc;
int irq;
+ irq_lock_sparse();
for_each_irq_desc(irq, desc) {
unsigned long flags;
bool sync;
@@ -146,6 +147,7 @@ void suspend_device_irqs(void)
if (sync)
synchronize_irq(irq);
}
+ irq_unlock_sparse();
}
EXPORT_SYMBOL_GPL(suspend_device_irqs);
@@ -186,6 +188,7 @@ static void resume_irqs(bool want_early)
struct irq_desc *desc;
int irq;
+ /* The early resume stage is free of irq_desc release */
for_each_irq_desc(irq, desc) {
unsigned long flags;
bool is_early = desc->action &&
--
2.31.1
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