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Date:   Fri, 15 Jun 2018 19:40:13 +0200
From:   Sebastian Sewior <bigeasy@linutronix.de>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Alan Stern <stern@rowland.harvard.edu>,
        Mikulas Patocka <mpatocka@redhat.com>,
        Ming Lei <ming.lei@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        USB list <linux-usb@vger.kernel.org>,
        Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: High-priority softirqs [was: [PATCH] usb: don't offload
 isochronous urb completions to ksoftirq]
Message-ID: <20180615174012.m6rqow2sytwgxxrx@linutronix.de>
References: <Pine.LNX.4.44L0.1806151308310.1387-100000@iolanthe.rowland.org>
 <alpine.DEB.2.21.1806151919130.1582@nanos.tec.linutronix.de>
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On 2018-06-15 13:34:28 [-0400], Steven Rostedt wrote:
> On Fri, 15 Jun 2018 19:28:34 +0200 (CEST)
> Thomas Gleixner <tglx@linutronix.de> wrote:
> 
> > One solution to that is to avoid both tasklets and kworkers and change the
> > USB code to make use of threaded interrupt handlers. I.e. handle the fast
> > stuff in the primary (hardirq) handler and delegate the rest to the irq
> > thread. That thread still can offload disk type stuff to a kworker if
> > needed. But the irq thread allows to bring the stuff under scheduler
> > control and experiments which I did a few years ago worked out pretty good.
> 
> If there's any question about this, drivers can request to have their
> interrupt handlers run as threads. This has been added to mainline
> years ago. And it really should be the default solution before pushing
> off to tasklets or kworkers.

 https://lkml.kernel.org/r/20180216170450.yl5owfphuvltstnt@breakpoint.cc

> -- Steve

Sebastian