Hi Pavan, On Tue, Oct 16, 2018 at 09:45:52AM +0530, Pavan Kondeti wrote: > Hi Frederic, > > On Thu, Oct 11, 2018 at 01:12:16AM +0200, Frederic Weisbecker wrote: > > From: Frederic Weisbecker <fweis...@gmail.com> > > > > Make do_softirq() re-entrant and allow a vector, being either processed > > or disabled, to be interrupted by another vector. This way a vector > > won't be able to monopolize the CPU for a long while at the expense of > > the others that may rely on some predictable latency, especially on > > softirq disabled sections that used to disable all vectors. > > > I understand that a long running softirq can be preempted/interrupted by > other softirqs which is not possible today. I have few questions on your > patches. > > (1) When softirq processing is pushed to ksoftirqd, then the long running > softirq can still block other softirqs (not in SOFTIRQ_NOW_MASK) for a while. > correct?
No, Ksoftirqd is treated the same as IRQ tail processing here: a vector can interrupt another. So for example, a NET_RX softirq running in Ksoftirqd can be interrupted by a TIMER softirq running in hardirq tail. > > (2) When softirqs processing happens asynchronously, a particular softirq > like TASKLET can keep interrupting an already running softirq like > TIMER/NET_RX, > correct? In worse case scenario, a long running softirq like NET_RX interrupt > a TIMER softirq. But I guess this is something expected with this. i.e > each softirq is independent and whichever comes recent gets to interrupt the > previously running softirqs. Exactly, and that's inherent with interrupts in general. The only way to work around that is to thread each vector independantly but that's a whole different dimension :-) Thanks!
