Re: [RFC PATCH 29/30] softirq: Make softirq processing softinterruptible

[Pavan Kondeti]

Hi Frederic,

On Thu, Oct 11, 2018 at 01:12:16AM +0200, Frederic Weisbecker wrote:
> From: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> 
> 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?

(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.

Thanks,
Pavan

-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.