Re: [PATCH v2] usb: dwc3: gadget: Replace list_for_each_entry_safe() if using giveback

Hi Wesley,

Wesley Cheng [off-list ref] writes:

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Sorry for the late response.  So I tried with a list_replace_init() to
within the list_for_each_entry_safe() loop to update tmp w/ the
cancelled_list list head, but the issue was still observed.  This is
because we can't replace the reference the loop already has stored in
tmp, which is simply updated as the current item on the next iteration.

I believe this is what you were trying to achieve?

Was wondering if you had any further inputs on this change?  As
mentioned, I tried a few things with list_replace_init(), which did not
work.

Sorry for the ping.  Is this change OK to add as is?  We've been running
into this instance pretty frequently during our testing, so just wanted
to close on the proper changes being merged upstream.

The idea is this:

	struct list_head	local;

        spin_lock_irq(&lock);
        list_replace_init(&dwc->cancelled_list, &local);
        spin_unlock_irq(&lock);

	list_for_each_entry_safe(req, tmp, &local, list) {
        	/* ... */
	}

It looks to me this should work fine, no? You can also follow what
drivers/usb/core/hcd.c is doing in usb_giveback_urb_bh() and restarting
if dwc->cancelled_list is not empty after list_for_each_entry_safe().

Can you give that one a shot?

Great, thanks for this suggestion!  Now I understand what you were
referring to.  I gave this a try and it works well.  Will prepare a
change to replace both places with list_replace_init()

this is great news :-) Thanks for trying it out

-- 
balbi