linux-kernel - Re: [PATCH v4 2/2] PCI/aer_inject: Convert inject_lock to raw_spinlock

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Message-ID: <20251103192120.GJ3419281@noisy.programming.kicks-ass.net>
Date: Mon, 3 Nov 2025 20:21:20 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Guangbo Cui <jckeep.cuiguangbo@...il.com>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Clark Williams <clrkwllms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Waiman Long <longman@...hat.com>, linux-rt-devel@...ts.linux.dev,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v4 2/2] PCI/aer_inject: Convert inject_lock to
 raw_spinlock_t

On Sun, Nov 02, 2025 at 10:57:06AM +0000, Guangbo Cui wrote:
> The AER injection path may run in interrupt-disabled context while
> holding inject_lock. On PREEMPT_RT kernels, spinlock_t becomes a
> sleeping lock, so it must not be taken while a raw_spinlock_t is held.
> Doing so violates lock ordering rules and trigger lockdep reports
> such as “Invalid wait context”.
> 
> Convert inject_lock to raw_spinlock_t to ensure non-sleeping locking
> semantics. The protected list is bounded and used only for debugging,
> so raw locking will not cause latency issues.

Bounded how?

Also,

---

--- a/drivers/pci/pcie/aer_inject.c
+++ b/drivers/pci/pcie/aer_inject.c
@@ -85,12 +85,13 @@ static void aer_error_init(struct aer_er
 	err->pos_cap_err = pos_cap_err;
 }
 
-/* inject_lock must be held before calling */
 static struct aer_error *__find_aer_error(u32 domain, unsigned int bus,
 					  unsigned int devfn)
 {
 	struct aer_error *err;
 
+	lockdep_assert_held(&inject_lock);
+
 	list_for_each_entry(err, &einjected, list) {
 		if (domain == err->domain &&
 		    bus == err->bus &&
@@ -100,20 +101,24 @@ static struct aer_error *__find_aer_erro
 	return NULL;
 }
 
-/* inject_lock must be held before calling */
 static struct aer_error *__find_aer_error_by_dev(struct pci_dev *dev)
 {
-	int domain = pci_domain_nr(dev->bus);
+	int domain;
+
+	lockdep_assert_held(&inject_lock);
+
+	domain = pci_domain_nr(dev->bus);
 	if (domain < 0)
 		return NULL;
 	return __find_aer_error(domain, dev->bus->number, dev->devfn);
 }
 
-/* inject_lock must be held before calling */
 static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus)
 {
 	struct pci_bus_ops *bus_ops;
 
+	lockdep_assert_held(&inject_lock);
+
 	list_for_each_entry(bus_ops, &pci_bus_ops_list, list) {
 		if (bus_ops->bus == bus)
 			return bus_ops->ops;