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Date: Mon, 29 Aug 2022 21:47:41 +0000 From: Thinh Nguyen <Thinh.Nguyen@...opsys.com> To: Sebastian Andrzej Siewior <bigeasy@...utronix.de> CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>, Felipe Balbi <balbi@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Dmitry Bogdanov <d.bogdanov@...ro.com>, "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>, "target-devel@...r.kernel.org" <target-devel@...r.kernel.org> Subject: Re: [PATCH v2 11/25] usb: gadget: f_tcm: Execute command on write completion On Mon, Aug 29, 2022, Sebastian Andrzej Siewior wrote: > On 2022-08-26 18:37:36 [+0000], Thinh Nguyen wrote: > > On Fri, Aug 26, 2022, Sebastian Andrzej Siewior wrote: > > > 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(): > > > > It will always be called with interrupts disabled as documented in > > usb_request API. > > > > > | 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; > > > > > > > Since target_execute_cmd() is called in usbg_data_write_cmpl(), > > interrupts are still disabled. > > but you do realize that target_execute_cmd() will leave with enabled > interrupts and this is not desired? I _think_ this was the reason why I > ended up with the wait+complete construct instead of invoking this > function directly. > An _irqsave() in target_execute_cmd() would probably be all you need > here. > Ok. Maybe we should make a change in the target_execute_cmd() then. It seems unreasonable to force the caller to workaround this such as the wait+complete construct you did (and I don't recall we have changes in place to know/guarantee that interrupts are enabled before executing target_execute_cmd() previously either). For the dwc3, we masked the interrupt at this point, so interrupt won't be asserted here. Thanks, Thinh
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