Messages in this thread | | | Date | Fri, 17 Sep 2021 18:06:06 +0300 | Subject | Re: [PATCH v7 19/19] staging: r8188eu: remove shared buffer for usb requests | From | Pavel Skripkin <> |
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On 9/17/21 18:03, Pavel Skripkin wrote: > On 9/17/21 17:55, Greg Kroah-Hartman wrote: >> On Fri, Sep 17, 2021 at 09:18:37AM +0200, Fabio M. De Francesco wrote: >>> From: Pavel Skripkin <paskripkin@gmail.com> >>> >>> This driver used shared buffer for usb requests. It led to using >>> mutexes, i.e no usb requests can be done in parallel. >>> >>> USB requests can be fired in parallel since USB Core allows it. In >>> order to allow them, remove usb_vendor_req_buf from dvobj_priv (since >>> USB I/O is the only user of it) and remove also usb_vendor_req_mutex >>> (since there is nothing to protect). >> >> Ah, you are removing this buffer, nice! >> >> But, just because the USB core allows multiple messages to be sent to a >> device at the same time, does NOT mean that the device itself can handle >> that sort of a thing. >> >> Keeping that lock might be a good idea, until you can prove otherwise. >> You never know, maybe there's never any contention at all for it because >> these accesses are all done in a serial fashion and the lock >> grab/release is instant. But if that is not the case, you might really >> get a device confused here by throwing multiple control messages at it >> in ways that it is not set up to handle at all. >> >> So please do not drop the lock. >> >> More comments below. >> > > We have tested this change. I've tested it in qemu with TP-Link > TL-WN722N v2 / v3 [Realtek RTL8188EUS], and Fabio has tested it on his > host for like a whole evening. > > I agree, that our testing does not cover all possible cases and I can't > say it was "good stress testing", so, I think, we need some comments > from maintainers. > > @Larry, @Phillip, does this change looks reasonable for this chip? > ^^^^^^^^^^^
I mean mutex removal, sorry for confusion :)
With regards, Pavel Skripkin
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