2018-01-26 08:45:17

by Jia-Ju Bai

Subject: [PATCH] opp: cpu: Replace GFP_ATOMIC with GFP_KERNEL in dev_pm_opp_init_cpufreq_table

After checking all possible call chains to
dev_pm_opp_init_cpufreq_table() here,
my tool finds that this function is never called in atomic context,
namely never in an interrupt handler or holding a spinlock.
And dev_pm_opp_init_cpufreq_table() calls dev_pm_opp_get_opp_count(),
which calls mutex_lock that can sleep.
It indicates that atmtcp_v_send() can call functions which may sleep.
Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL.

This is found by a static analysis tool named DCNS written by myself.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
drivers/opp/cpu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/opp/cpu.c b/drivers/opp/cpu.c
index 2d87bc1..0c09107 100644
--- a/drivers/opp/cpu.c
+++ b/drivers/opp/cpu.c
@@ -55,7 +55,7 @@ int dev_pm_opp_init_cpufreq_table(struct device *dev,
if (max_opps <= 0)
return max_opps ? max_opps : -ENODATA;

- freq_table = kcalloc((max_opps + 1), sizeof(*freq_table), GFP_ATOMIC);
+ freq_table = kcalloc((max_opps + 1), sizeof(*freq_table), GFP_KERNEL);
if (!freq_table)
return -ENOMEM;

--
1.7.9.5

2018-02-08 14:46:28

by Viresh Kumar

Subject: Re: [PATCH] opp: cpu: Replace GFP_ATOMIC with GFP_KERNEL in dev_pm_opp_init_cpufreq_table

On 26-01-18, 16:48, Jia-Ju Bai wrote:
> After checking all possible call chains to
> dev_pm_opp_init_cpufreq_table() here,
> my tool finds that this function is never called in atomic context,
> namely never in an interrupt handler or holding a spinlock.
> And dev_pm_opp_init_cpufreq_table() calls dev_pm_opp_get_opp_count(),
> which calls mutex_lock that can sleep.
> It indicates that atmtcp_v_send() can call functions which may sleep.
> Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL.
>
> This is found by a static analysis tool named DCNS written by myself.
>
> Signed-off-by: Jia-Ju Bai <[email protected]>
> ---
> drivers/opp/cpu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/opp/cpu.c b/drivers/opp/cpu.c
> index 2d87bc1..0c09107 100644
> --- a/drivers/opp/cpu.c
> +++ b/drivers/opp/cpu.c
> @@ -55,7 +55,7 @@ int dev_pm_opp_init_cpufreq_table(struct device *dev,
> if (max_opps <= 0)
> return max_opps ? max_opps : -ENODATA;
>
> - freq_table = kcalloc((max_opps + 1), sizeof(*freq_table), GFP_ATOMIC);
> + freq_table = kcalloc((max_opps + 1), sizeof(*freq_table), GFP_KERNEL);
> if (!freq_table)
> return -ENOMEM;

Applied thanks.

--
viresh