It was found that the following circular locking dependency warning could happen in some systems:
[ 218.097878] ====================================================== [ 218.097879] WARNING: possible circular locking dependency detected [ 218.097880] 4.18.0-228.el8.x86_64+debug #1 Not tainted [ 218.097881] ------------------------------------------------------ [ 218.097882] systemd/1 is trying to acquire lock: [ 218.097883] ffffffff84c27920 (console_owner){-.-.}, at: console_unlock+0x3fb/0x9f0 [ 218.097886] [ 218.097887] but task is already holding lock: [ 218.097888] ffffffff84afca78 (vector_lock){-.-.}, at: x86_vector_activate+0xca/0xab0 [ 218.097891] [ 218.097892] which lock already depends on the new lock. : [ 218.097966] other info that might help us debug this: [ 218.097967] [ 218.097967] Chain exists of: [ 218.097968] console_oc_lock_class --> vector_lock [ 218.097972] [ 218.097973] Possible unsafe locking scenario: [ 218.097973] [ 218.097974] CPU0 CPU1 [ 218.097975] ---- ---- [ 218.097975] lock(vector_lock); [ 218.097977] lock(&irq_desc_lock_class); [ 218.097980] lock(vector_lock); [ 218.097981] lock(console_owner); [ 218.097983] [ 218.097984] *** DEADLOCK *** This lockdep warning was causing by printing of the warning message: [ 218.095152] irq 3: Affinity broken due to vector space exhaustion. It looks that this warning message is relatively more common than the other warnings in arch/x86/kernel/apic/vector.c. To avoid this potential deadlock scenario, this patch moves all the pr_warn() calls in the vector.c file outside of the vector_lock critical sections. Signed-off-by: Waiman Long <long...@redhat.com> --- arch/x86/kernel/apic/vector.c | 33 ++++++++++++++++++++------------- 1 file changed, 20 insertions(+), 13 deletions(-) diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c index 3c9c7492252f..948ec592ef61 100644 --- a/arch/x86/kernel/apic/vector.c +++ b/arch/x86/kernel/apic/vector.c @@ -385,7 +385,8 @@ static void x86_vector_deactivate(struct irq_domain *dom, struct irq_data *irqd) raw_spin_unlock_irqrestore(&vector_lock, flags); } -static int activate_reserved(struct irq_data *irqd) +static int activate_reserved(struct irq_data *irqd, unsigned long flags, + bool *unlocked) { struct apic_chip_data *apicd = apic_chip_data(irqd); int ret; @@ -410,6 +411,8 @@ static int activate_reserved(struct irq_data *irqd) */ if (!cpumask_subset(irq_data_get_effective_affinity_mask(irqd), irq_data_get_affinity_mask(irqd))) { + raw_spin_unlock_irqrestore(&vector_lock, flags); + *unlocked = true; pr_warn("irq %u: Affinity broken due to vector space exhaustion.\n", irqd->irq); } @@ -446,6 +449,7 @@ static int x86_vector_activate(struct irq_domain *dom, struct irq_data *irqd, { struct apic_chip_data *apicd = apic_chip_data(irqd); unsigned long flags; + bool unlocked = false; int ret = 0; trace_vector_activate(irqd->irq, apicd->is_managed, @@ -459,8 +463,9 @@ static int x86_vector_activate(struct irq_domain *dom, struct irq_data *irqd, else if (apicd->is_managed) ret = activate_managed(irqd); else if (apicd->has_reserved) - ret = activate_reserved(irqd); - raw_spin_unlock_irqrestore(&vector_lock, flags); + ret = activate_reserved(irqd, flags, &unlocked); + if (!unlocked) + raw_spin_unlock_irqrestore(&vector_lock, flags); return ret; } @@ -989,6 +994,7 @@ void irq_force_complete_move(struct irq_desc *desc) struct apic_chip_data *apicd; struct irq_data *irqd; unsigned int vector; + bool warn_move_in_progress = false; /* * The function is called for all descriptors regardless of which @@ -1064,12 +1070,14 @@ void irq_force_complete_move(struct irq_desc *desc) * so we have the necessary information when a problem in that * area arises. */ - pr_warn("IRQ fixup: irq %d move in progress, old vector %d\n", - irqd->irq, vector); + warn_move_in_progress = true; } free_moved_vector(apicd); unlock: raw_spin_unlock(&vector_lock); + if (warn_move_in_progress) + pr_warn("IRQ fixup: irq %d move in progress, old vector %d\n", + irqd->irq, vector); } #ifdef CONFIG_HOTPLUG_CPU @@ -1079,25 +1087,24 @@ void irq_force_complete_move(struct irq_desc *desc) */ int lapic_can_unplug_cpu(void) { - unsigned int rsvd, avl, tomove, cpu = smp_processor_id(); + unsigned int rsvd = 0, avl, tomove, cpu = smp_processor_id(); int ret = 0; raw_spin_lock(&vector_lock); tomove = irq_matrix_allocated(vector_matrix); avl = irq_matrix_available(vector_matrix, true); + if (avl < tomove) + ret = -ENOSPC; + else + rsvd = irq_matrix_reserved(vector_matrix); + raw_spin_unlock(&vector_lock); if (avl < tomove) { pr_warn("CPU %u has %u vectors, %u available. Cannot disable CPU\n", cpu, tomove, avl); - ret = -ENOSPC; - goto out; - } - rsvd = irq_matrix_reserved(vector_matrix); - if (avl < rsvd) { + } else if (avl < rsvd) { pr_warn("Reserved vectors %u > available %u. IRQ request may fail\n", rsvd, avl); } -out: - raw_spin_unlock(&vector_lock); return ret; } #endif /* HOTPLUG_CPU */ -- 2.18.1