linux-kernel - Re: [PATCH 3/3] riscv: Allow to enable PREEMPT

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Message-ID: <20241009174153.Hk5MGakp@linutronix.de>
Date: Wed, 9 Oct 2024 19:41:53 +0200
From: Nam Cao <namcao@...utronix.de>
To: Palmer Dabbelt <palmer@...belt.com>
Cc: bigeasy@...utronix.de, tglx@...utronix.de,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, x86@...nel.org, hpa@...or.com,
	aou@...s.berkeley.edu, bp@...en8.de,
	Catalin Marinas <catalin.marinas@....com>, williams@...hat.com,
	dave.hansen@...ux.intel.com, mingo@...hat.com,
	john.ogness@...utronix.de, Paul Walmsley <paul.walmsley@...ive.com>,
	pmladek@...e.com, senozhatsky@...omium.org, rostedt@...dmis.org,
	Will Deacon <will@...nel.org>
Subject: Re: [PATCH 3/3] riscv: Allow to enable PREEMPT_RT.

On Wed, Oct 09, 2024 at 09:44:59AM -0700, Palmer Dabbelt wrote:
> On Fri, 06 Sep 2024 11:48:03 PDT (-0700), Palmer Dabbelt wrote:
> > On Fri, 06 Sep 2024 08:13:24 PDT (-0700), namcao@...utronix.de wrote:
> > > On Fri, Sep 06, 2024 at 12:59:06PM +0200, Sebastian Andrzej Siewior wrote:
> > > > It is really time.
> > > > 
> > > > riscv has all the required architecture related changes, that have been
> > > > identified over time, in order to enable PREEMPT_RT. With the recent
> > > > printk changes, the last known road block has been addressed.
> > > > 
> > > > Allow to enable PREEMPT_RT on riscv.
> > > > 
> > > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> > > 
> > > With the printk patches applied:
> > > 
> > > Tested-by: Nam Cao <namcao@...utronix.de> # Visionfive 2
> > 
> > 
> > Thanks.  LMK if you guys want me to take this through the RISC-V tree,
> > but no big deal if you want it somewhere else -- and if there's some
> > dependencies already going in through some sort of RT tree maybe that's
> > just easier.  So
> > 
> > Acked-by: Palmer Dabbelt <palmer@...osinc.com>
> > 
> > I don't have a test setup yet, but I figure it's a new feature so I'll
> > just flip it on as a config post-rc1.  Presumably this just works in the
> > QEMU virt board, or is there some wizardry I'll need to copy?
> 
> and it breaks my boot test script.  Looks like it's actually working mostly
> fine, I'm just not getting the "reboot: System halted" message that I'm
> checking for to make sure the system actually went down cleanly.
> 
> I'm not sure if this is expected behavior in RT land, or if we've got some
> sort of bug.  It sort of smells like we're losing the last printk() line...

I also had some occasional problem with rebooting my Visionfive 2 board,
which was fixed with:
https://lore.kernel.org/lkml/20241003084152.2422969-1-namcao@linutronix.de/

Any chance this fixes your issue as well?

Best regards,
Nam