* [PATCH] cpufreq: exynos5440: Protect opp search calls with rcu lock
@ 2013-04-15 6:24 Amit Daniel Kachhap
2013-04-15 14:10 ` Nishanth Menon
2013-04-21 23:32 ` Rafael J. Wysocki
0 siblings, 2 replies; 4+ messages in thread
From: Amit Daniel Kachhap @ 2013-04-15 6:24 UTC (permalink / raw)
To: linux-pm, Rafael J. Wysocki
Cc: linux-kernel, linux-samsung-soc, linux-arm-kernel, Kukjin Kim,
cpufreq, Nishanth Menon
As per the OPP library documentation(Documentation/power/opp.txt) all
opp find/get calls should be protected by rcu locks.
Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
---
This patch is created against linux-next tree and is suggested by
Nishanth Menon. (https://lkml.org/lkml/2013/4/12/119)
drivers/cpufreq/exynos5440-cpufreq.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/drivers/cpufreq/exynos5440-cpufreq.c b/drivers/cpufreq/exynos5440-cpufreq.c
index ead7ed4..0c74018 100644
--- a/drivers/cpufreq/exynos5440-cpufreq.c
+++ b/drivers/cpufreq/exynos5440-cpufreq.c
@@ -120,11 +120,13 @@ static int init_div_table(void)
int i = 0;
struct opp *opp;
+ rcu_read_lock();
for (i = 0; freq_tbl[i].frequency != CPUFREQ_TABLE_END; i++) {
opp = opp_find_freq_exact(dvfs_info->dev,
freq_tbl[i].frequency * 1000, true);
if (IS_ERR(opp)) {
+ rcu_read_unlock();
dev_err(dvfs_info->dev,
"failed to find valid OPP for %u KHZ\n",
freq_tbl[i].frequency);
@@ -159,6 +161,7 @@ static int init_div_table(void)
__raw_writel(tmp, dvfs_info->base + XMU_PMU_P0_7 + 4 * i);
}
+ rcu_read_unlock();
return 0;
}
--
1.7.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] cpufreq: exynos5440: Protect opp search calls with rcu lock
2013-04-15 6:24 [PATCH] cpufreq: exynos5440: Protect opp search calls with rcu lock Amit Daniel Kachhap
@ 2013-04-15 14:10 ` Nishanth Menon
2013-04-16 6:51 ` amit daniel kachhap
2013-04-21 23:32 ` Rafael J. Wysocki
1 sibling, 1 reply; 4+ messages in thread
From: Nishanth Menon @ 2013-04-15 14:10 UTC (permalink / raw)
To: Amit Daniel Kachhap
Cc: linux-pm, Rafael J. Wysocki, Kukjin Kim, lkml, cpufreq,
linux-samsung-soc, linux-arm-kernel@lists.infradead.org
Daniel,
On Mon, Apr 15, 2013 at 1:24 AM, Amit Daniel Kachhap
<amit.daniel@samsung.com> wrote:
> As per the OPP library documentation(Documentation/power/opp.txt) all
> opp find/get calls should be protected by rcu locks.
>
> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
> ---
>
> This patch is created against linux-next tree and is suggested by
> Nishanth Menon. (https://lkml.org/lkml/2013/4/12/119)
>
> drivers/cpufreq/exynos5440-cpufreq.c | 3 +++
> 1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/cpufreq/exynos5440-cpufreq.c b/drivers/cpufreq/exynos5440-cpufreq.c
> index ead7ed4..0c74018 100644
> --- a/drivers/cpufreq/exynos5440-cpufreq.c
> +++ b/drivers/cpufreq/exynos5440-cpufreq.c
> @@ -120,11 +120,13 @@ static int init_div_table(void)
> int i = 0;
> struct opp *opp;
>
> + rcu_read_lock();
> for (i = 0; freq_tbl[i].frequency != CPUFREQ_TABLE_END; i++) {
>
> opp = opp_find_freq_exact(dvfs_info->dev,
> freq_tbl[i].frequency * 1000, true);
> if (IS_ERR(opp)) {
> + rcu_read_unlock();
> dev_err(dvfs_info->dev,
> "failed to find valid OPP for %u KHZ\n",
> freq_tbl[i].frequency);
> @@ -159,6 +161,7 @@ static int init_div_table(void)
> __raw_writel(tmp, dvfs_info->base + XMU_PMU_P0_7 + 4 * i);
> }
>
> + rcu_read_unlock();
Is it not possible to reduce the amount of code protected by RCU lock?
something like this:
+ rcu_read_lock();
opp = opp_find_freq_exact(dvfs_info->dev,
freq_tbl[i].frequency * 1000, true);
if (IS_ERR(opp)) {
+ rcu_read_unlock();
dev_err(dvfs_info->dev,
"failed to find valid OPP for %u KHZ\n",
freq_tbl[i].frequency);
return PTR_ERR(opp);
}
+ volt_id = opp_get_voltage(opp);
+ rcu_unlock();
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] cpufreq: exynos5440: Protect opp search calls with rcu lock
2013-04-15 14:10 ` Nishanth Menon
@ 2013-04-16 6:51 ` amit daniel kachhap
0 siblings, 0 replies; 4+ messages in thread
From: amit daniel kachhap @ 2013-04-16 6:51 UTC (permalink / raw)
To: Nishanth Menon
Cc: linux-samsung-soc, linux-pm, lkml, cpufreq, Rafael J. Wysocki,
Kukjin Kim, linux-arm-kernel@lists.infradead.org
Hi Nishanth,
Thanks for reviewing this patch.
On Mon, Apr 15, 2013 at 7:40 PM, Nishanth Menon <nm@ti.com> wrote:
> Daniel,
> On Mon, Apr 15, 2013 at 1:24 AM, Amit Daniel Kachhap
> <amit.daniel@samsung.com> wrote:
>> As per the OPP library documentation(Documentation/power/opp.txt) all
>> opp find/get calls should be protected by rcu locks.
>>
>> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
>> ---
>>
>> This patch is created against linux-next tree and is suggested by
>> Nishanth Menon. (https://lkml.org/lkml/2013/4/12/119)
>>
>> drivers/cpufreq/exynos5440-cpufreq.c | 3 +++
>> 1 files changed, 3 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/cpufreq/exynos5440-cpufreq.c b/drivers/cpufreq/exynos5440-cpufreq.c
>> index ead7ed4..0c74018 100644
>> --- a/drivers/cpufreq/exynos5440-cpufreq.c
>> +++ b/drivers/cpufreq/exynos5440-cpufreq.c
>> @@ -120,11 +120,13 @@ static int init_div_table(void)
>> int i = 0;
>> struct opp *opp;
>>
>> + rcu_read_lock();
>> for (i = 0; freq_tbl[i].frequency != CPUFREQ_TABLE_END; i++) {
>>
>> opp = opp_find_freq_exact(dvfs_info->dev,
>> freq_tbl[i].frequency * 1000, true);
>> if (IS_ERR(opp)) {
>> + rcu_read_unlock();
>> dev_err(dvfs_info->dev,
>> "failed to find valid OPP for %u KHZ\n",
>> freq_tbl[i].frequency);
>> @@ -159,6 +161,7 @@ static int init_div_table(void)
>> __raw_writel(tmp, dvfs_info->base + XMU_PMU_P0_7 + 4 * i);
>> }
>>
>> + rcu_read_unlock();
>
> Is it not possible to reduce the amount of code protected by RCU lock?
> something like this:
Yes it is possible but then this part of code is a loop of max 8
iteration so rcu_read_lock will be called those many times.
Also this code blocks are just register writes and not doing any time
consuming operations.
Thanks,
Amit Daniel
> + rcu_read_lock();
> opp = opp_find_freq_exact(dvfs_info->dev,
> freq_tbl[i].frequency * 1000, true);
> if (IS_ERR(opp)) {
> + rcu_read_unlock();
> dev_err(dvfs_info->dev,
> "failed to find valid OPP for %u KHZ\n",
> freq_tbl[i].frequency);
> return PTR_ERR(opp);
> }
> + volt_id = opp_get_voltage(opp);
> + rcu_unlock();
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] cpufreq: exynos5440: Protect opp search calls with rcu lock
2013-04-15 6:24 [PATCH] cpufreq: exynos5440: Protect opp search calls with rcu lock Amit Daniel Kachhap
2013-04-15 14:10 ` Nishanth Menon
@ 2013-04-21 23:32 ` Rafael J. Wysocki
1 sibling, 0 replies; 4+ messages in thread
From: Rafael J. Wysocki @ 2013-04-21 23:32 UTC (permalink / raw)
To: Amit Daniel Kachhap
Cc: linux-pm, linux-kernel, linux-samsung-soc, linux-arm-kernel,
Kukjin Kim, cpufreq, Nishanth Menon
On Monday, April 15, 2013 11:54:47 AM Amit Daniel Kachhap wrote:
> As per the OPP library documentation(Documentation/power/opp.txt) all
> opp find/get calls should be protected by rcu locks.
>
> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
> ---
>
> This patch is created against linux-next tree and is suggested by
> Nishanth Menon. (https://lkml.org/lkml/2013/4/12/119)
Applied.
Thanks,
Rafael
> drivers/cpufreq/exynos5440-cpufreq.c | 3 +++
> 1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/cpufreq/exynos5440-cpufreq.c b/drivers/cpufreq/exynos5440-cpufreq.c
> index ead7ed4..0c74018 100644
> --- a/drivers/cpufreq/exynos5440-cpufreq.c
> +++ b/drivers/cpufreq/exynos5440-cpufreq.c
> @@ -120,11 +120,13 @@ static int init_div_table(void)
> int i = 0;
> struct opp *opp;
>
> + rcu_read_lock();
> for (i = 0; freq_tbl[i].frequency != CPUFREQ_TABLE_END; i++) {
>
> opp = opp_find_freq_exact(dvfs_info->dev,
> freq_tbl[i].frequency * 1000, true);
> if (IS_ERR(opp)) {
> + rcu_read_unlock();
> dev_err(dvfs_info->dev,
> "failed to find valid OPP for %u KHZ\n",
> freq_tbl[i].frequency);
> @@ -159,6 +161,7 @@ static int init_div_table(void)
> __raw_writel(tmp, dvfs_info->base + XMU_PMU_P0_7 + 4 * i);
> }
>
> + rcu_read_unlock();
> return 0;
> }
>
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2013-04-15 6:24 [PATCH] cpufreq: exynos5440: Protect opp search calls with rcu lock Amit Daniel Kachhap
2013-04-15 14:10 ` Nishanth Menon
2013-04-16 6:51 ` amit daniel kachhap
2013-04-21 23:32 ` Rafael J. Wysocki
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