From: Grygorii Strashko <grygorii.strashko@ti.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Lina Iyer <lina.iyer@linaro.org>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
Mark Rutland <mark.rutland@arm.com>,
ulf.hansson@linaro.org,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
linux-pm@vger.kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
rjw@rjwysocki.net, k.kozlowski@samsung.com,
msivasub@codeaurora.org, khilman@linaro.org,
geert@linux-m68k.org, agross@codeaurora.org,
sboyd@codeaurora.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 7/7] ARM: smp: Add runtime PM support for CPU hotplug
Date: Sat, 5 Sep 2015 00:46:37 +0300 [thread overview]
Message-ID: <55EA113D.9000806@ti.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1509041443360.29995-100000@iolanthe.rowland.org>
On 09/04/2015 09:45 PM, Alan Stern wrote:
> On Fri, 4 Sep 2015, Grygorii Strashko wrote:
>
>> There is one "small" problem with such approach :(
>>
>> - It's incompatible with -RT kernel, because PM runtime can't be used
>> in atomic context on -RT.
>
> Can you explain this more fully? Why can't runtime PM be used in
> atomic context in the -rt kernels?
>
See:
http://lwn.net/Articles/146861/
https://rt.wiki.kernel.org/index.php/Frequently_Asked_Questions#How_does_the_CONFIG_PREEMPT_RT_patch_work.3F
spinlock_t
Critical sections are preemptible. The _irq operations (e.g., spin_lock_irqsave())
do -not- disable hardware interrupts. Priority inheritance is used to prevent priority
inversion. An underlying rt_mutex is used to implement spinlock_t in PREEMPT_RT.
As result, have to do things like:
https://lkml.org/lkml/2015/8/18/161
https://lkml.org/lkml/2015/8/18/162
Sorry for brief reply - Friday/Sat night :)
--
regards,
-grygorii
WARNING: multiple messages have this Message-ID (diff)
From: grygorii.strashko@ti.com (Grygorii Strashko)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 7/7] ARM: smp: Add runtime PM support for CPU hotplug
Date: Sat, 5 Sep 2015 00:46:37 +0300 [thread overview]
Message-ID: <55EA113D.9000806@ti.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1509041443360.29995-100000@iolanthe.rowland.org>
On 09/04/2015 09:45 PM, Alan Stern wrote:
> On Fri, 4 Sep 2015, Grygorii Strashko wrote:
>
>> There is one "small" problem with such approach :(
>>
>> - It's incompatible with -RT kernel, because PM runtime can't be used
>> in atomic context on -RT.
>
> Can you explain this more fully? Why can't runtime PM be used in
> atomic context in the -rt kernels?
>
See:
http://lwn.net/Articles/146861/
https://rt.wiki.kernel.org/index.php/Frequently_Asked_Questions#How_does_the_CONFIG_PREEMPT_RT_patch_work.3F
spinlock_t
Critical sections are preemptible. The _irq operations (e.g., spin_lock_irqsave())
do -not- disable hardware interrupts. Priority inheritance is used to prevent priority
inversion. An underlying rt_mutex is used to implement spinlock_t in PREEMPT_RT.
As result, have to do things like:
https://lkml.org/lkml/2015/8/18/161
https://lkml.org/lkml/2015/8/18/162
Sorry for brief reply - Friday/Sat night :)
--
regards,
-grygorii
next prev parent reply other threads:[~2015-09-04 21:47 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-03 19:58 [PATCH v2 0/7] PM / Domains: Generic PM domains for CPUs/Clusters Lina Iyer
2015-09-03 19:58 ` Lina Iyer
2015-09-03 19:58 ` [PATCH v2 1/7] PM / Domains: Allocate memory outside domain locks Lina Iyer
2015-09-03 19:58 ` Lina Iyer
2015-09-03 19:58 ` [PATCH v2 2/7] PM / Domains: Support IRQ safe PM domains Lina Iyer
2015-09-03 19:58 ` Lina Iyer
2015-09-04 10:02 ` Ulf Hansson
2015-09-04 10:02 ` Ulf Hansson
2015-09-04 16:05 ` Lina Iyer
2015-09-04 16:05 ` Lina Iyer
2015-10-01 21:11 ` Geert Uytterhoeven
2015-10-01 21:11 ` Geert Uytterhoeven
2015-09-03 19:58 ` [PATCH v2 3/7] drivers: cpu: Define CPU devices as IRQ safe Lina Iyer
2015-09-03 19:58 ` Lina Iyer
2015-09-04 4:00 ` Stephen Boyd
2015-09-04 4:00 ` Stephen Boyd
2015-09-03 19:58 ` [PATCH v2 4/7] PM / Domains: Introduce PM domains for CPUs/clusters Lina Iyer
2015-09-03 19:58 ` Lina Iyer
2015-09-04 3:54 ` Stephen Boyd
2015-09-04 3:54 ` Stephen Boyd
2015-09-03 19:58 ` [PATCH v2 5/7] ARM: cpuidle: Add runtime PM support for CPU idle Lina Iyer
2015-09-03 19:58 ` Lina Iyer
2015-09-03 19:58 ` [PATCH v2 6/7] ARM64: smp: Add runtime PM support for CPU hotplug Lina Iyer
2015-09-03 19:58 ` Lina Iyer
2015-09-30 12:36 ` Geert Uytterhoeven
2015-09-30 12:36 ` Geert Uytterhoeven
2015-09-03 19:58 ` [PATCH v2 7/7] ARM: " Lina Iyer
2015-09-03 19:58 ` Lina Iyer
2015-09-04 3:59 ` Stephen Boyd
2015-09-04 3:59 ` Stephen Boyd
2015-09-04 15:13 ` Lina Iyer
2015-09-04 15:13 ` Lina Iyer
2015-09-04 7:39 ` Geert Uytterhoeven
2015-09-04 7:39 ` Geert Uytterhoeven
2015-09-04 9:17 ` Russell King - ARM Linux
2015-09-04 9:17 ` Russell King - ARM Linux
2015-09-04 9:27 ` Russell King - ARM Linux
2015-09-04 9:27 ` Russell King - ARM Linux
2015-09-04 15:12 ` Lina Iyer
2015-09-04 15:12 ` Lina Iyer
2015-09-04 16:23 ` Russell King - ARM Linux
2015-09-04 16:23 ` Russell King - ARM Linux
2015-09-04 17:02 ` Lina Iyer
2015-09-04 17:02 ` Lina Iyer
2015-09-04 17:46 ` Russell King - ARM Linux
2015-09-04 17:46 ` Russell King - ARM Linux
2015-09-04 17:57 ` Grygorii Strashko
2015-09-04 17:57 ` Grygorii Strashko
2015-09-04 18:45 ` Alan Stern
2015-09-04 18:45 ` Alan Stern
2015-09-04 21:46 ` Grygorii Strashko [this message]
2015-09-04 21:46 ` Grygorii Strashko
2015-09-05 15:39 ` Alan Stern
2015-09-05 15:39 ` Alan Stern
2015-09-07 13:04 ` Rafael J. Wysocki
2015-09-07 13:04 ` Rafael J. Wysocki
2015-09-07 13:37 ` Grygorii Strashko
2015-09-07 13:37 ` Grygorii Strashko
2015-09-07 20:42 ` Rafael J. Wysocki
2015-09-07 20:42 ` Rafael J. Wysocki
2015-09-08 8:21 ` Grygorii Strashko
2015-09-08 8:21 ` Grygorii Strashko
2015-09-08 22:03 ` Kevin Hilman
2015-09-08 22:03 ` Kevin Hilman
2015-09-10 11:01 ` Grygorii Strashko
2015-09-10 11:01 ` Grygorii Strashko
2015-09-22 17:32 ` Lina Iyer
2015-09-22 17:32 ` Lina Iyer
2015-09-22 20:53 ` Thomas Gleixner
2015-09-22 20:53 ` Thomas Gleixner
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