Messages in this thread | | | Date | Fri, 17 Sep 2021 18:23:23 +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 18:18, Greg Kroah-Hartman wrote: > On Fri, Sep 17, 2021 at 06:03:52PM +0300, 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. > > Ok, then make it a single patch that does nothing but remove the lock so > that we can revert it later when problems show up :) >
Sure! Thank you again :)
With regards, Pavel Skripkin
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