Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Vincent Whitchurch <> | Date | Thu, 15 Jun 2023 15:11:57 +0200 | Subject | [PATCH] genirq: Fix nested thread vs synchronize_hardirq() deadlock |
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There is a possibility of deadlock if synchronize_hardirq() is called when the nested threaded interrupt is active. The following scenario was observed on a uniprocessor PREEMPT_NONE system:
Thread 1 Thread 2
handle_nested_thread() Set INPROGRESS Call ->thread_fn() thread_fn goes to sleep
free_irq() __synchronize_hardirq() Busy-loop forever waiting for INPROGRESS to be cleared
Since the purpose of the INPROGRESS flag seems to be for hard IRQ handlers, remove its usage in the nested threaded interrupt case and instead re-use the active_threads mechanism to wait for nested threaded interrupts to complete.
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> --- kernel/irq/chip.c | 5 +++-- kernel/irq/manage.c | 4 ++++ 2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c index 49e7bc871fece..3e4b4c6de8195 100644 --- a/kernel/irq/chip.c +++ b/kernel/irq/chip.c @@ -476,7 +476,7 @@ void handle_nested_irq(unsigned int irq) } kstat_incr_irqs_this_cpu(desc); - irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS); + atomic_inc(&desc->threads_active); raw_spin_unlock_irq(&desc->lock); action_ret = IRQ_NONE; @@ -487,7 +487,8 @@ void handle_nested_irq(unsigned int irq) note_interrupt(desc, action_ret); raw_spin_lock_irq(&desc->lock); - irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS); + if (atomic_dec_and_test(&desc->threads_active)) + wake_up(&desc->wait_for_threads); out_unlock: raw_spin_unlock_irq(&desc->lock); diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index d2742af0f0fd8..58dcc9df6d72c 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -1977,6 +1977,10 @@ static struct irqaction *__free_irq(struct irq_desc *desc, void *dev_id) } } + /* Wait for any remaining nested threaded interrupts. */ + wait_event(desc->wait_for_threads, + !atomic_read(&desc->threads_active)); + /* Last action releases resources */ if (!desc->action) { /* --- base-commit: 858fd168a95c5b9669aac8db6c14a9aeab446375 change-id: 20230613-genirq-nested-625612a6fa05 Best regards, -- Vincent Whitchurch <vincent.whitchurch@axis.com>
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