On sam., 2016-02-27 at 18:10 -0800, Peter Hurley wrote: > On 02/27/2016 05:59 PM, Eric Dumazet wrote: > > On sam., 2016-02-27 at 15:33 -0800, Peter Hurley wrote: > >> On 02/27/2016 03:04 PM, David Miller wrote: > >>> From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> > >>> Date: Sat, 27 Feb 2016 12:29:39 -0800 > >>> > >>>> Not really. softirq raised from interrupt context will always execute > >>>> on this cpu and not in ksoftirqd, unless load forces softirq loop abort. > >>> > >>> That guarantee never was specified. > >> > >> ?? > >> > >> Neither is running network socket servers at normal priority as if they're > >> higher priority than softirq. > >> > >> > >>> Or are you saying that by design, on a system under load, your UART > >>> will not function properly? > >>> > >>> Surely you don't mean that. > >> > >> No, that's not what I mean. > >> > >> What I mean is that bypassing the entire SOFTIRQ priority so that > >> sshd can process one network packet makes a mockery of the point of softirq. > >> > >> This hack to workaround NET_RX looping over-and-over-and-over affects every > >> subsystem, not just one uart. > >> > >> HI, TIMER, BLOCK; all of these are skipped: that's straight-up, a bug. > > > > No idea what you talk about. > > > > All pending softirq interrupts are processed. _Nothing_ is skipped. > > An interrupt that schedules HI softirq while in NET_RX softirq should > still run the HI softirq. But with your patch that won't happen. Stop saying this. This never had been the case. I am glad my patch finally show you are wrong. > > > > Really, your system stability seems to depend on a completely > > undocumented behavior of linux kernels before linux-3.8 > > > > If I understood, you expect that a tasklet activated from a softirq > > handler is run from the same __do_softirq() loop. This never has been > > the case. > > No. > > The *interrupt handler* for DMA goes off while NET_RX softirq is running. > That's what schedules the *DMA tasklet*. > > That tasklet should run before any process. > > But it doesn't because your patch bails out early from softirq. Fine. Fix your driver. -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
