On Sun, Dec 25, 2011 at 1:48 AM, Eyal Shapira <eyal@xxxxxxxxxx> wrote: > > > > On Fri, Dec 23, 2011 at 10:46 AM, Luciano Coelho <coelho@xxxxxx> wrote: >> >> On Wed, 2011-12-21 at 16:10 +0100, Johannes Berg wrote: >> > On Wed, 2011-12-21 at 12:11 +0200, Eyal Shapira wrote: >> > > Changes in mac/cfg80211 to notify userspace >> > > of NL80211_CMD_SCHED_SCAN_STOPPED only when the driver >> > > actually reported back that it was stopped. Also >> > > blocks other attempts until we're really done. >> > > >> > > This fixes a scenario where stop sched scan >> > > is issued and immediately afterwards a new sched scan >> > > is requested (e.g. with other parameters). >> > > Current state caused a race where the driver started >> > > stopping the sched scan but didn't finish and got >> > > another sched scan request which it couldn't handle. >> > >> > Luca really needs to take a close look at this, and I think you should >> > also take a look to see if this kind of API change can be avoided. >> >> I had discussed this with Eyal briefly and at first it seemed ok. But >> actually I now agree that this is an API change. >> >> Looking closer, I see that in the current documentation, there's nothing >> stating that after sending sched_scan_stop the userspace needs to wait >> for the stopped event. It just says that "[this] event is also sent >> when the %NL80211_CMD_STOP_SCHED_SCAN command is received [...]". >> Applications may assume that after the stop command completes, it is >> really stopped, without waiting for the stopped event. >> >> Could the code be changed so that we delay the STOP_SCHED_SCAN command >> completion instead? Then userspace can rely on that (as it should >> anyway, because the command can fail) instead of having to wait for the >> stopped event (which is a change in the API). >> > Sounds like this would be the best way to go and I'll do that. So no need > for these patches. I misunderstood the STOP_SCHED_SCAN NL API to be async (due to the NL events) but it can and should be synchronous AFAIU. > (and might sleep / block). > > The only mac80211 change I'd be glad to add is to make sched_scan_stop op return > a value so errors can be reported back like it's being done in the sched_scan_stop cfg80211 op > >> -- >> Cheers, >> Luca. >> > -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
