linux-kernel - [PATCH] x86: Fix RCU list usage to avoid false positive warnings

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Message-Id: <20200430192932.13371-1-madhuparnabhowmik10@gmail.com>
Date:   Fri,  1 May 2020 00:59:32 +0530
From:   madhuparnabhowmik10@...il.com
To:     mingo@...hat.com, pbonzini@...hat.com, bp@...en8.de
Cc:     x86@...nel.org, bhelgaas@...gle.com,
        sean.j.christopherson@...el.com, cai@....pw, paulmck@...nel.org,
        joel@...lfernandes.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        frextrite@...il.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-pci@...r.kernel.org,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
Subject: [PATCH] x86: Fix RCU list usage to avoid false positive warnings

From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

Use list_for_each_entry() instead of list_for_each_entry_rcu() whenever
spinlock or mutex is always held.
Otherwise, pass cond to list_for_each_entry_rcu().

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
---
 arch/x86/kernel/nmi.c          | 2 +-
 arch/x86/kvm/irq_comm.c        | 3 ++-
 arch/x86/pci/mmconfig-shared.c | 2 +-
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 6407ea21fa1b..999dc6c134d2 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -195,7 +195,7 @@ void unregister_nmi_handler(unsigned int type, const char *name)
 
 	raw_spin_lock_irqsave(&desc->lock, flags);
 
-	list_for_each_entry_rcu(n, &desc->head, list) {
+	list_for_each_entry(n, &desc->head, list) {
 		/*
 		 * the name passed in to describe the nmi handler
 		 * is used as the lookup key
diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index c47d2acec529..5b88a648e079 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -258,7 +258,8 @@ void kvm_fire_mask_notifiers(struct kvm *kvm, unsigned irqchip, unsigned pin,
 	idx = srcu_read_lock(&kvm->irq_srcu);
 	gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
 	if (gsi != -1)
-		hlist_for_each_entry_rcu(kimn, &kvm->arch.mask_notifier_list, link)
+		hlist_for_each_entry_rcu(kimn, &kvm->arch.mask_notifier_list, link,
+					srcu_read_lock_held(&kvm->irq_srcu))
 			if (kimn->irq == gsi)
 				kimn->func(kimn, mask);
 	srcu_read_unlock(&kvm->irq_srcu, idx);
diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c
index 6fa42e9c4e6f..a096942690bd 100644
--- a/arch/x86/pci/mmconfig-shared.c
+++ b/arch/x86/pci/mmconfig-shared.c
@@ -797,7 +797,7 @@ int pci_mmconfig_delete(u16 seg, u8 start, u8 end)
 	struct pci_mmcfg_region *cfg;
 
 	mutex_lock(&pci_mmcfg_lock);
-	list_for_each_entry_rcu(cfg, &pci_mmcfg_list, list)
+	list_for_each_entry(cfg, &pci_mmcfg_list, list)
 		if (cfg->segment == seg && cfg->start_bus == start &&
 		    cfg->end_bus == end) {
 			list_del_rcu(&cfg->list);
-- 
2.17.1