On Tue, Sep 17, 2019 at 7:10 PM Tony Chuang <yhchuang@xxxxxxxxxxx> wrote: > > On Mon, Sep 16, 2019 at 12:03 AM <yhchuang@xxxxxxxxxxx> wrote: > > > > > > From: Yan-Hsuan Chuang <yhchuang@xxxxxxxxxxx> > > > > > > Interrupt is disabled to stop PCI, which means the skbs > > > queued for each TX ring will not be released via DMA > > > interrupt. > > > > In what cases do you hit this? I think you do this when entering PS > > mode, no? But then, see below. > > I'll hit this when ieee80211_ops::stop, or rtw_power_off. > Both are to turn off the device, so there's no more DMA activities. > If we don't release the SKBs that are not released by DMA interrupt > when powering off, these could be leaked. Ah, I was a bit confused. So it does get called from "PS" routines: rtw_enter_ips() -> rtw_core_stop() but that "IPS" mode means "Inactive" Power Save, and it's only used when transitioning into idle states (IEEE80211_CONF_IDLE). Incidentally, I think this also may explain many of the leaks I've been seeing elsewhere, when I leave a device sitting and scanning for a very long time -- each scan attempt is making a single transition out-and-back to IPS mode, which meant it may be leaking any outstanding TX DMA. And testing confirms this: if I just bring up the interface, run a scan, then bring it down, I see many fewer unmaps than maps. Doing this enough times, I run out of contiguous DMA memory and the device stops working. This fixes that problem for me. So: Reviewed-by: Brian Norris <briannorris@xxxxxxxxxxxx> Tested-by: Brian Norris <briannorris@xxxxxxxxxxxx> I wonder if, given the problems I've seen (the driver can become totally ineroperable), this patch and the previous patch (its only real dependency) should be fast-tracked to the current release. Brian
