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From: Catalin Marinas <catalin.marinas@arm.com>
To: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	linux-kernel@vger.kernel.org, sudeep.holla@arm.com,
	will@kernel.org, morten.rasmussen@arm.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: abort counter_read_on_cpu() when irqs_disabled()
Date: Fri, 13 Nov 2020 19:55:33 +0000	[thread overview]
Message-ID: <20201113195532.GA20519@gaia> (raw)
In-Reply-To: <20201113165843.GA6973@arm.com>

On Fri, Nov 13, 2020 at 04:58:43PM +0000, Ionela Voinescu wrote:
> On Friday 13 Nov 2020 at 16:02:34 (+0000), Mark Rutland wrote:
> > On Fri, Nov 13, 2020 at 03:53:28PM +0000, Ionela Voinescu wrote:
> > > Given that smp_call_function_single() can deadlock when interrupts are
> > > disabled, abort the SMP call if irqs_disabled(). This scenario is
> > > currently not possible given the function's uses, but safeguard this for
> > > potential future uses.
> > 
> > Sorry to contradict earlier feedback, but I think this is preferable
> > as-is, since smp_call_function_single() will
> > WARN_ON_ONCE(irqs_disabled())), but this will silently mask any dodgy
> > usage.
> 
> Probably it only contradicts the chosen implementation.
> 
> > If we want a separate check here, I reckon we should wrap it with a
> > WARN_ON_ONCE(), and only relax that if/when we have a legitimate case
> > for calling this with IRQs disabled.
> > 
> 
> That's fair. I'll replace the condition below with:
> 
> 	if (!cpu_has_amu_feat(cpu))
> 		return -EOPNOTSUPP;
> 
> 	if (WARN_ON_ONCE(irqs_disabled())
> 		return -EPERM;

Works for me. Thanks.

-- 
Catalin

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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	sudeep.holla@arm.com, will@kernel.org, morten.rasmussen@arm.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: abort counter_read_on_cpu() when irqs_disabled()
Date: Fri, 13 Nov 2020 19:55:33 +0000	[thread overview]
Message-ID: <20201113195532.GA20519@gaia> (raw)
In-Reply-To: <20201113165843.GA6973@arm.com>

On Fri, Nov 13, 2020 at 04:58:43PM +0000, Ionela Voinescu wrote:
> On Friday 13 Nov 2020 at 16:02:34 (+0000), Mark Rutland wrote:
> > On Fri, Nov 13, 2020 at 03:53:28PM +0000, Ionela Voinescu wrote:
> > > Given that smp_call_function_single() can deadlock when interrupts are
> > > disabled, abort the SMP call if irqs_disabled(). This scenario is
> > > currently not possible given the function's uses, but safeguard this for
> > > potential future uses.
> > 
> > Sorry to contradict earlier feedback, but I think this is preferable
> > as-is, since smp_call_function_single() will
> > WARN_ON_ONCE(irqs_disabled())), but this will silently mask any dodgy
> > usage.
> 
> Probably it only contradicts the chosen implementation.
> 
> > If we want a separate check here, I reckon we should wrap it with a
> > WARN_ON_ONCE(), and only relax that if/when we have a legitimate case
> > for calling this with IRQs disabled.
> > 
> 
> That's fair. I'll replace the condition below with:
> 
> 	if (!cpu_has_amu_feat(cpu))
> 		return -EOPNOTSUPP;
> 
> 	if (WARN_ON_ONCE(irqs_disabled())
> 		return -EPERM;

Works for me. Thanks.

-- 
Catalin

  parent reply	other threads:[~2020-11-13 19:57 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-06 12:53 [PATCH v4 0/3] arm64: cppc: add FFH support using AMUs Ionela Voinescu
2020-11-06 12:53 ` Ionela Voinescu
2020-11-06 12:53 ` [PATCH v4 1/3] arm64: wrap and generalise counter read functions Ionela Voinescu
2020-11-06 12:53   ` Ionela Voinescu
2020-11-13 14:11   ` Sudeep Holla
2020-11-13 14:11     ` Sudeep Holla
2020-11-06 12:53 ` [PATCH v4 2/3] arm64: split counter validation function Ionela Voinescu
2020-11-06 12:53   ` Ionela Voinescu
2020-11-13 14:12   ` Sudeep Holla
2020-11-13 14:12     ` Sudeep Holla
2020-11-06 12:53 ` [PATCH v4 3/3] arm64: implement CPPC FFH support using AMUs Ionela Voinescu
2020-11-06 12:53   ` Ionela Voinescu
2020-11-12 18:00   ` Catalin Marinas
2020-11-12 18:00     ` Catalin Marinas
2020-11-13 12:28     ` Ionela Voinescu
2020-11-13 12:28       ` Ionela Voinescu
2020-11-13 12:54       ` Catalin Marinas
2020-11-13 12:54         ` Catalin Marinas
2020-11-13 14:16   ` Sudeep Holla
2020-11-13 14:16     ` Sudeep Holla
2020-11-13 16:37     ` Ionela Voinescu
2020-11-13 16:37       ` Ionela Voinescu
2020-11-13 20:03       ` Catalin Marinas
2020-11-13 20:03         ` Catalin Marinas
2020-11-13 15:53 ` [PATCH] arm64: abort counter_read_on_cpu() when irqs_disabled() Ionela Voinescu
2020-11-13 15:53   ` Ionela Voinescu
2020-11-13 16:02   ` Mark Rutland
2020-11-13 16:02     ` Mark Rutland
2020-11-13 16:58     ` Ionela Voinescu
2020-11-13 16:58       ` Ionela Voinescu
2020-11-13 17:30       ` Mark Rutland
2020-11-13 17:30         ` Mark Rutland
2020-11-13 19:55       ` Catalin Marinas [this message]
2020-11-13 19:55         ` Catalin Marinas
2020-11-13 20:26 ` [PATCH v4 0/3] arm64: cppc: add FFH support using AMUs Catalin Marinas
2020-11-13 20:26   ` Catalin Marinas

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