linux-kernel - Re: [PATCH v2 11/25] usb: gadget: f_tcm: Execute command on write completion

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Date:   Fri, 26 Aug 2022 09:00:42 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dmitry Bogdanov <d.bogdanov@...ro.com>,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org
Subject: Re: [PATCH v2 11/25] usb: gadget: f_tcm: Execute command on write
 completion

On 2022-07-18 18:27:12 [-0700], Thinh Nguyen wrote:
> index 6fea80afe2d7..ec83f2f9a858 100644
> --- a/drivers/usb/gadget/function/f_tcm.c
> +++ b/drivers/usb/gadget/function/f_tcm.c
> @@ -955,7 +949,7 @@ static void usbg_data_write_cmpl(struct usb_ep *ep, struct usb_request *req)
>  				se_cmd->data_length);
>  	}
>  
> -	complete(&cmd->write_complete);
> +	target_execute_cmd(se_cmd);

usbg_data_write_cmpl() is invoked from interrupt service routing which
may run with disabled interrupts. From looking at target_execute_cmd():
| void target_execute_cmd(struct se_cmd *cmd)
| {
…
|         spin_lock_irq(&cmd->t_state_lock);
…
|         spin_unlock_irq(&cmd->t_state_lock);
…
| }

which means interrupts will remain open after leaving
target_execute_cmd(). Now, why didn't the WARN_ONCE() in
__handle_irq_event_percpu() trigger? Am I missing something?

>  	return;

Sebastian