From: Arnd Bergmann <arnd@kernel.org>
To: "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>
Cc: "tglx@linutronix.de" <tglx@linutronix.de>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"arnd@arndb.de" <arnd@arndb.de>,
"geert@linux-m68k.org" <geert@linux-m68k.org>,
"funaho@jurai.org" <funaho@jurai.org>,
"philb@gnu.org" <philb@gnu.org>,
"corbet@lwn.net" <corbet@lwn.net>,
"mingo@redhat.com" <mingo@redhat.com>,
"linux-m68k@lists.linux-m68k.org"
<linux-m68k@lists.linux-m68k.org>,
"fthain@telegraphics.com.au" <fthain@telegraphics.com.au>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] IRQ handlers run with some high-priority interrupts(not NMI) enabled on some platform
Date: Sat, 13 Feb 2021 00:05:43 +0100 [thread overview]
Message-ID: <CAK8P3a0fwMe9LaXMfKjH46yvt6o-euZJZ4HXtVRPhYbKvAUPKg@mail.gmail.com> (raw)
In-Reply-To: <24e0652b3afa48cdbf7c83287e43c087@hisilicon.com>
On Sat, Feb 13, 2021 at 12:00 AM Song Bao Hua (Barry Song)
<song.bao.hua@hisilicon.com> wrote:
> > -----Original Message-----
> > From: Arnd Bergmann [mailto:arnd@kernel.org]
> > Sent: Saturday, February 13, 2021 11:34 AM
> > To: Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com>
> > Cc: tglx@linutronix.de; gregkh@linuxfoundation.org; arnd@arndb.de;
> > geert@linux-m68k.org; funaho@jurai.org; philb@gnu.org; corbet@lwn.net;
> > mingo@redhat.com; linux-m68k@lists.linux-m68k.org;
> > fthain@telegraphics.com.au; linux-kernel@vger.kernel.org
> > Subject: Re: [RFC] IRQ handlers run with some high-priority interrupts(not NMI)
> > enabled on some platform
> >
> > On Fri, Feb 12, 2021 at 2:18 AM Song Bao Hua (Barry Song)
> > <song.bao.hua@hisilicon.com> wrote:
> >
> > > So I am requesting comments on:
> > > 1. are we expecting all interrupts except NMI to be disabled in irq handler,
> > > or do we actually allow some high-priority interrupts between low and NMI
> > to
> > > come in some platforms?
> >
> > I tried to come to an answer but this does not seem particularly well-defined.
> > There are a few things I noticed:
> >
> > - going through the local_irq_save()/restore() implementations on all
> > architectures, I did not find any other ones besides m68k that leave
> > high-priority interrupts enabled. I did see that at least alpha and openrisc
> > are designed to support that in hardware, but the code just leaves the
> > interrupts disabled.
>
> The case is a little different. Explicit local_irq_save() does disable all
> high priority interrupts on m68k. The only difference is arch_irqs_disabled()
> of m68k will return true while low-priority interrupts are masked and high
> -priority are still open. M68k's hardIRQ also runs in this context with high
> priority interrupts enabled.
My point was that on most other architectures, local_irq_save()/restore()
always disables/enables all interrupts, while on m68k it restores the
specific level they were on before. On alpha, it does the same as on m68k,
but then the top-level interrupt handler just disables them all before calling
into any other code.
It's possible that I missed some other implementation doing the same
as m68k, as this code is fairly subtle on some architectures.
Arnd
next prev parent reply other threads:[~2021-02-12 23:06 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-12 1:18 [RFC] IRQ handlers run with some high-priority interrupts(not NMI) enabled on some platform Song Bao Hua (Barry Song)
2021-02-12 22:34 ` Arnd Bergmann
2021-02-12 23:00 ` Song Bao Hua (Barry Song)
2021-02-12 23:05 ` Arnd Bergmann [this message]
2021-02-12 23:46 ` Song Bao Hua (Barry Song)
2021-02-13 16:32 ` Arnd Bergmann
2021-02-13 22:18 ` Song Bao Hua (Barry Song)
2021-02-13 23:18 ` Song Bao Hua (Barry Song)
2021-02-14 5:10 ` Finn Thain
2021-02-15 13:06 ` Andy Shevchenko
2021-02-15 22:22 ` Finn Thain
2021-02-17 22:41 ` Song Bao Hua (Barry Song)
2021-02-18 5:30 ` Finn Thain
2021-02-18 11:19 ` Arnd Bergmann
2021-02-18 12:30 ` Geert Uytterhoeven
2021-02-18 13:59 ` Arnd Bergmann
2021-02-18 15:38 ` Geert Uytterhoeven
2021-02-18 22:11 ` Michael Schmitz
2021-02-19 8:10 ` Geert Uytterhoeven
2021-02-19 22:30 ` Brad Boyer
2021-02-20 6:32 ` Finn Thain
2021-02-20 7:08 ` Brad Boyer
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