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usb: gadget: u_serial: Avoid spinlock recursion in __gs_console_push
When serial console over USB is enabled, gs_console_connect queues gs_console_work, where it acquires the spinlock and queues the usb request, and this request goes to gadget layer. Now consider a situation where gadget layer prints something to dmesg, this will eventually call gs_console_write() which requires cons->lock. And this causes spinlock recursion. Avoid this by excluding usb_ep_queue from the spinlock. spin_lock_irqsave //needs cons->lock gs_console_write . . _printk __warn_printk dev_warn/pr_err . . [USB Gadget Layer] . . usb_ep_queue gs_console_work __gs_console_push // acquires cons->lock process_one_work Signed-off-by: Prashanth K <quic_prashk@quicinc.com> Link: https://lore.kernel.org/r/1683638872-6885-1-git-send-email-quic_prashk@quicinc.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -916,8 +916,11 @@ static void __gs_console_push(struct gs_console *cons)
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}
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req->length = size;
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spin_unlock_irq(&cons->lock);
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if (usb_ep_queue(ep, req, GFP_ATOMIC))
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req->length = 0;
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spin_lock_irq(&cons->lock);
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}
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static void gs_console_work(struct work_struct *work)
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