* [Fwd: [patch] intel_idle: Delete meaningless local_irq_disable() call in intel_idle.c.]
@ 2011-12-26 1:28 Yanmin Zhang
2011-12-28 0:10 ` Andrew Morton
0 siblings, 1 reply; 3+ messages in thread
From: Yanmin Zhang @ 2011-12-26 1:28 UTC (permalink / raw)
To: akpm; +Cc: LKML, shaohua.li, len.brown, mingmingx.zhang
Andrew,
Would you like to accept the patch into your testing tree?
Thanks,
Yanmin
-------- Forwarded Message --------
From: Zhang, MingmingX <mingmingx.zhang@intel.com>
To: linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>
Cc: yanmin_zhang@linux.intel.com <yanmin_zhang@linux.intel.com>, Li,
Shaohua <shaohua.li@intel.com>, Brown, Len <len.brown@intel.com>
Subject: [patch] intel_idle: Delete meaningless local_irq_disable() call
in intel_idle.c.
Date: Fri, 23 Dec 2011 01:57:29 +0000
From: mzha38X <mingmingx.zhang@intel.com>
intel_idle.c is a bit misleading in a sense that local_irq_disable,it
actually does nothing. Real irq disable happens earlier in process_32.c:cpu_idle.
Basically, cpuidle_state->enter is called, cpu irq is disabled.
cpuidle_state->enter would turn on irq when exiting.
intel_idle doesn't follow this assumption. Although it doesn't
cause real issue, it misleads developers. Below patch deletes
the calling to local_irq_disable() at entry.
Signed-off-by: mzha38X <mingmingx.zhang@intel.com>
---
drivers/idle/intel_idle.c | 2 --
1 files changed, 0 insertions(+), 2 deletions(-)
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 5d2f8e1..28f0394 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -247,8 +247,6 @@ static int intel_idle(struct cpuidle_device *dev,
cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1;
- local_irq_disable();
-
/*
* leave_mm() to avoid costly and often unnecessary wakeups
* for flushing the user TLB's associated with the active mm.
--
1.7.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [Fwd: [patch] intel_idle: Delete meaningless local_irq_disable() call in intel_idle.c.]
2011-12-26 1:28 [Fwd: [patch] intel_idle: Delete meaningless local_irq_disable() call in intel_idle.c.] Yanmin Zhang
@ 2011-12-28 0:10 ` Andrew Morton
2011-12-28 0:27 ` Yanmin Zhang
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2011-12-28 0:10 UTC (permalink / raw)
To: yanmin_zhang; +Cc: LKML, shaohua.li, len.brown, mingmingx.zhang
On Mon, 26 Dec 2011 09:28:20 +0800
Yanmin Zhang <yanmin_zhang@linux.intel.com> wrote:
> Andrew,
>
> Would you like to accept the patch into your testing tree?
hm, that's three indel_idle patches which I have now. Someone wake up
lenb!
> intel_idle.c is a bit misleading in a sense that local_irq_disable,it
> actually does nothing. Real irq disable happens earlier in process_32.c:cpu_idle.
> Basically, cpuidle_state->enter is called, cpu irq is disabled.
> cpuidle_state->enter would turn on irq when exiting.
>
> intel_idle doesn't follow this assumption. Although it doesn't
> cause real issue, it misleads developers. Below patch deletes
> the calling to local_irq_disable() at entry.
>
> Signed-off-by: mzha38X <mingmingx.zhang@intel.com>
> ---
> drivers/idle/intel_idle.c | 2 --
> 1 files changed, 0 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index 5d2f8e1..28f0394 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -247,8 +247,6 @@ static int intel_idle(struct cpuidle_device *dev,
>
> cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1;
>
> - local_irq_disable();
> -
> /*
> * leave_mm() to avoid costly and often unnecessary wakeups
> * for flushing the user TLB's associated with the active mm.
I'd suggest adding this as well:
--- a/drivers/idle/intel_idle.c~drivers-idle-intel_idlec-remove-redundant-local_irq_disable-call-fix
+++ a/drivers/idle/intel_idle.c
@@ -232,6 +232,7 @@ static int get_driver_data(int cstate)
* @drv: cpuidle driver
* @index: index of cpuidle state
*
+ * Must be called under local_irq_disable().
*/
static int intel_idle(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index)
_
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Fwd: [patch] intel_idle: Delete meaningless local_irq_disable() call in intel_idle.c.]
2011-12-28 0:10 ` Andrew Morton
@ 2011-12-28 0:27 ` Yanmin Zhang
0 siblings, 0 replies; 3+ messages in thread
From: Yanmin Zhang @ 2011-12-28 0:27 UTC (permalink / raw)
To: Andrew Morton; +Cc: LKML, shaohua.li, len.brown, mingmingx.zhang
On Tue, 2011-12-27 at 16:10 -0800, Andrew Morton wrote:
> On Mon, 26 Dec 2011 09:28:20 +0800
> Yanmin Zhang <yanmin_zhang@linux.intel.com> wrote:
>
> > Andrew,
> >
> > Would you like to accept the patch into your testing tree?
>
> hm, that's three indel_idle patches which I have now. Someone wake up
> lenb!
>
> > intel_idle.c is a bit misleading in a sense that local_irq_disable,it
>
> I'd suggest adding this as well:
Agree. It'll be clearer.
>
> --- a/drivers/idle/intel_idle.c~drivers-idle-intel_idlec-remove-redundant-local_irq_disable-call-fix
> +++ a/drivers/idle/intel_idle.c
> @@ -232,6 +232,7 @@ static int get_driver_data(int cstate)
> * @drv: cpuidle driver
> * @index: index of cpuidle state
> *
> + * Must be called under local_irq_disable().
> */
> static int intel_idle(struct cpuidle_device *dev,
> struct cpuidle_driver *drv, int index)
^ permalink raw reply [flat|nested] 3+ messages in thread
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2011-12-26 1:28 [Fwd: [patch] intel_idle: Delete meaningless local_irq_disable() call in intel_idle.c.] Yanmin Zhang
2011-12-28 0:10 ` Andrew Morton
2011-12-28 0:27 ` Yanmin Zhang
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