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From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Arnd Bergmann <arnd@kernel.org>
Cc: v.narang@samsung.com, a.sahrawat@samsung.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Marc Zyngier <maz@kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Vincent Whitchurch <vincent.whitchurch@axis.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Dmitry Safonov <0x7f454c46@gmail.com>,
	Maninder Singh <maninder1.s@samsung.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Nathan Huckleberry <nhuck@google.com>,
	Will Deacon <will@kernel.org>, Jian Cai <caij2003@gmail.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 2/3] arm: introduce IRQ stacks
Date: Wed, 21 Oct 2020 13:45:42 +0100	[thread overview]
Message-ID: <20201021124542.GL1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <CAK8P3a3eZjBVSuhv=Cx4aYC+E9tex+BbJH1b6YyMMief-mO7kQ@mail.gmail.com>

On Wed, Oct 21, 2020 at 02:42:48PM +0200, Arnd Bergmann wrote:
> (also resending this reply from @kernel.org)
> 
> On Fri, Oct 16, 2020 at 12:19 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > On Thu, Oct 8, 2020 at 9:20 AM Maninder Singh <maninder1.s@samsung.com> wrote:
> > >
> > > This patch adds code for switching to IRQ stack.
> > > IRQ stack and Kernel SVC stack have below design.
> > >
> > > IRQ STACK:-
> > >                     ------------ IRQ stack top
> > >                     |          |
> > >                     ------------
> > >                     .          .
> > >                     .          .
> > >                     .          .
> > >                     ------------
> > >                     |    sp    | <- irq_stack_base + 0x8
> > >                     ------------
> > >                     |    fp    | <- irq_stack_base + 0x4
> > >                     ------------
> > >                     |tinfo_ptr | /* pointer to thread info */
> > > irq_stack_ptr -->   ------------ IRQ stack base
> > >
> > > Kernel SVC stack:-
> > >                     ------------  Kernel stack top
> > >                     |          |
> > >                     ------------
> > >                     .          .
> > >                     .          .
> > >                     .          .
> > >                     ------------
> > >                     |          |
> > >                     |          |
> > >                     ------------
> > >                     |tinfo_ptr |  /* pointer to thread info */
> > >                     ------------ Kernel stack base
> >
> > The extra indirection doesn't look great, and I don't see any of the
> > other architectures need that. Since we can access percpu data
> > without going through thread_info, maybe doing the same as
> > x86 would work here:
> >
> > - define 'current' as 'this_cpu_read_stable(current_task);'
> > - convert to CONFIG_THREAD_INFO_IN_TASK

That means we need to also code that up in assembly - remember, we
need to access thread_info from assembly code.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

_______________________________________________
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WARNING: multiple messages have this Message-ID (diff)
From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Maninder Singh <maninder1.s@samsung.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Jian Cai <caij2003@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Marc Zyngier <maz@kernel.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Vincent Whitchurch <vincent.whitchurch@axis.com>,
	Nathan Huckleberry <nhuck@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dmitry Safonov <0x7f454c46@gmail.com>,
	Will Deacon <will@kernel.org>,
	v.narang@samsung.com, a.sahrawat@samsung.com,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 2/3] arm: introduce IRQ stacks
Date: Wed, 21 Oct 2020 13:45:42 +0100	[thread overview]
Message-ID: <20201021124542.GL1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <CAK8P3a3eZjBVSuhv=Cx4aYC+E9tex+BbJH1b6YyMMief-mO7kQ@mail.gmail.com>

On Wed, Oct 21, 2020 at 02:42:48PM +0200, Arnd Bergmann wrote:
> (also resending this reply from @kernel.org)
> 
> On Fri, Oct 16, 2020 at 12:19 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > On Thu, Oct 8, 2020 at 9:20 AM Maninder Singh <maninder1.s@samsung.com> wrote:
> > >
> > > This patch adds code for switching to IRQ stack.
> > > IRQ stack and Kernel SVC stack have below design.
> > >
> > > IRQ STACK:-
> > >                     ------------ IRQ stack top
> > >                     |          |
> > >                     ------------
> > >                     .          .
> > >                     .          .
> > >                     .          .
> > >                     ------------
> > >                     |    sp    | <- irq_stack_base + 0x8
> > >                     ------------
> > >                     |    fp    | <- irq_stack_base + 0x4
> > >                     ------------
> > >                     |tinfo_ptr | /* pointer to thread info */
> > > irq_stack_ptr -->   ------------ IRQ stack base
> > >
> > > Kernel SVC stack:-
> > >                     ------------  Kernel stack top
> > >                     |          |
> > >                     ------------
> > >                     .          .
> > >                     .          .
> > >                     .          .
> > >                     ------------
> > >                     |          |
> > >                     |          |
> > >                     ------------
> > >                     |tinfo_ptr |  /* pointer to thread info */
> > >                     ------------ Kernel stack base
> >
> > The extra indirection doesn't look great, and I don't see any of the
> > other architectures need that. Since we can access percpu data
> > without going through thread_info, maybe doing the same as
> > x86 would work here:
> >
> > - define 'current' as 'this_cpu_read_stable(current_task);'
> > - convert to CONFIG_THREAD_INFO_IN_TASK

That means we need to also code that up in assembly - remember, we
need to access thread_info from assembly code.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

  reply	other threads:[~2020-10-21 12:47 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20201008071628epcas5p24d196a6023a47a3b0bfa7b7f231ec811@epcas5p2.samsung.com>
2020-10-08  7:15 ` [PATCH 0/3] IRQ stack support for ARM Maninder Singh
2020-10-08  7:15   ` Maninder Singh
2020-10-08  7:15   ` [PATCH 1/3] arm: introduce self pointer in thread info Maninder Singh
2020-10-08  7:15     ` Maninder Singh
2020-10-08  7:15   ` [PATCH 2/3] arm: introduce IRQ stacks Maninder Singh
2020-10-08  7:15     ` Maninder Singh
     [not found]     ` <CAK8P3a2RYeNiTy9QmwFVKtFifXxWc9XfAT6ThPoSH9wGYsKGpA@mail.gmail.com>
2020-10-21 12:42       ` Arnd Bergmann
2020-10-21 12:42         ` Arnd Bergmann
2020-10-21 12:45         ` Russell King - ARM Linux admin [this message]
2020-10-21 12:45           ` Russell King - ARM Linux admin
2020-10-21 12:55           ` Arnd Bergmann
2020-10-21 12:55             ` Arnd Bergmann
2020-10-21 12:57           ` Russell King - ARM Linux admin
2020-10-21 12:57             ` Russell King - ARM Linux admin
2020-10-21 13:46             ` Vaneet Narang
2020-10-21 13:46               ` Vaneet Narang
2020-10-21 15:59             ` Arnd Bergmann
2020-10-21 15:59               ` Arnd Bergmann
2020-11-09 14:45               ` Tony Lindgren
2020-11-09 14:45                 ` Tony Lindgren
2020-11-09 19:10                 ` Arnd Bergmann
2020-11-09 19:10                   ` Arnd Bergmann
2020-11-10  9:19                   ` Tony Lindgren
2020-11-10  9:19                     ` Tony Lindgren
2020-11-10 10:04                     ` Arnd Bergmann
2020-11-10 10:04                       ` Arnd Bergmann
2020-11-10 12:04                       ` Tony Lindgren
2020-11-10 12:04                         ` Tony Lindgren
2020-11-10 13:35                         ` Arnd Bergmann
2020-11-10 13:35                           ` Arnd Bergmann
2020-11-11  6:56                           ` Tony Lindgren
2020-11-11  6:56                             ` Tony Lindgren
2020-10-08  7:15   ` [PATCH 3/3] arm: Modify stack trace and dump for use with irq stack Maninder Singh
2020-10-08  7:15     ` Maninder Singh
2020-10-08  7:53   ` [PATCH 0/3] IRQ stack support for ARM Sebastian Andrzej Siewior
2020-10-08  7:53     ` Sebastian Andrzej Siewior
2020-10-08  8:30   ` Russell King - ARM Linux admin
2020-10-08  8:30     ` Russell King - ARM Linux admin
2020-10-15 20:59     ` Nick Desaulniers
2020-10-15 20:59       ` Nick Desaulniers
2020-10-15 21:16       ` Florian Fainelli
2020-10-15 21:16         ` Florian Fainelli
     [not found]     ` <CAK8P3a0h=D8_Kn_fpHbsik_jf4to2jayxj7K7B7=HaNFzKqNnw@mail.gmail.com>
2020-10-21 11:58       ` Arnd Bergmann
2020-10-21 11:58         ` Arnd Bergmann
2020-10-21 12:34         ` Russell King - ARM Linux admin
2020-10-21 12:34           ` Russell King - ARM Linux admin
2020-10-21 12:46           ` Arnd Bergmann
2020-10-21 12:46             ` Arnd Bergmann
2020-10-08 13:04 [PATCH 2/3] arm: introduce IRQ stacks kernel test robot

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