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Message-ID: <20150521124833.GJ6776@linux.vnet.ibm.com>
Date: Thu, 21 May 2015 05:48:33 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Will Deacon <will.deacon@....com>
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<linux-arm-kernel@...ts.infradead.org>,
Catalin Marinas <Catalin.Marinas@....com>
Subject: Re: [PATCH tip/core/rcu 7/9] arm64: Use common
outgoing-CPU-notification code
On Thu, May 21, 2015 at 09:58:06AM +0100, Will Deacon wrote:
> Hi Paul,
>
> Sorry for being late on this one.
No problem! In fact, just in time -- I was going to bug you about
this later today. ;-)
> On Tue, May 12, 2015 at 10:50:05PM +0100, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
> >
> > This commit removes the open-coded CPU-offline notification with new
> > common code. In particular, this change avoids calling scheduler code
> > using RCU from an offline CPU that RCU is ignoring. This is a minimal
> > change. A more intrusive change might invoke the cpu_check_up_prepare()
> > and cpu_set_state_online() functions at CPU-online time, which would
> > allow onlining throw an error if the CPU did not go offline properly.
> >
> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > Cc: linux-arm-kernel@...ts.infradead.org
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: Will Deacon <will.deacon@....com>
> > ---
> > arch/arm64/kernel/smp.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
>
> I don't have a better idea, so:
>
> Acked-by: Will Deacon <will.deacon@....com>
>
> Is this queued via -tip already, or can we pick it into the arm64 tree
> for 4.2?
Feel free to take it into the arm64 tree. Just let me know, and I
will drop it from my tree.
Now I only need to bug the arm32 guys. ;-)
Thanx, Paul
> Cheers,
>
> Will
>
> > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> > index 2cb008177252..a899c1beff54 100644
> > --- a/arch/arm64/kernel/smp.c
> > +++ b/arch/arm64/kernel/smp.c
> > @@ -253,15 +253,13 @@ static int op_cpu_kill(unsigned int cpu)
> > return cpu_ops[cpu]->cpu_kill(cpu);
> > }
> >
> > -static DECLARE_COMPLETION(cpu_died);
> > -
> > /*
> > * called on the thread which is asking for a CPU to be shutdown -
> > * waits until shutdown has completed, or it is timed out.
> > */
> > void __cpu_die(unsigned int cpu)
> > {
> > - if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) {
> > + if (!cpu_wait_death(cpu, 5)) {
> > pr_crit("CPU%u: cpu didn't die\n", cpu);
> > return;
> > }
> > @@ -294,7 +292,7 @@ void cpu_die(void)
> > local_irq_disable();
> >
> > /* Tell __cpu_die() that this CPU is now safe to dispose of */
> > - complete(&cpu_died);
> > + (void)cpu_report_death();
> >
> > /*
> > * Actually shutdown the CPU. This must never fail. The specific hotplug
> > --
> > 1.8.1.5
> >
>
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