* [PATCH] net: decnet: Replace GFP_ATOMIC with GFP_KERNEL in dn_route_init
@ 2018-04-09 14:10 Jia-Ju Bai
2018-04-09 14:44 ` Eric Dumazet
0 siblings, 1 reply; 3+ messages in thread
From: Jia-Ju Bai @ 2018-04-09 14:10 UTC (permalink / raw)
To: davem, kafai, weiwan, dsa, johannes.berg, fw
Cc: linux-decnet-user, netdev, linux-kernel, Jia-Ju Bai
dn_route_init() is never called in atomic context.
The call chain ending up at dn_route_init() is:
[1] dn_route_init() <- decnet_init()
decnet_init() is only set as a parameter of module_init().
Despite never getting called from atomic context,
dn_route_init() calls __get_free_pages() with GFP_ATOMIC,
which waits busily for allocation.
GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
to avoid busy waiting and improve the possibility of sucessful allocation.
This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
net/decnet/dn_route.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index 0bd3afd..59ed12a 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -1898,7 +1898,7 @@ void __init dn_route_init(void)
while(dn_rt_hash_mask & (dn_rt_hash_mask - 1))
dn_rt_hash_mask--;
dn_rt_hash_table = (struct dn_rt_hash_bucket *)
- __get_free_pages(GFP_ATOMIC, order);
+ __get_free_pages(GFP_KERNEL, order);
} while (dn_rt_hash_table == NULL && --order > 0);
if (!dn_rt_hash_table)
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] net: decnet: Replace GFP_ATOMIC with GFP_KERNEL in dn_route_init
2018-04-09 14:10 [PATCH] net: decnet: Replace GFP_ATOMIC with GFP_KERNEL in dn_route_init Jia-Ju Bai
@ 2018-04-09 14:44 ` Eric Dumazet
2018-04-09 14:48 ` Jia-Ju Bai
0 siblings, 1 reply; 3+ messages in thread
From: Eric Dumazet @ 2018-04-09 14:44 UTC (permalink / raw)
To: Jia-Ju Bai, davem, kafai, weiwan, dsa, johannes.berg, fw
Cc: linux-decnet-user, netdev, linux-kernel
On 04/09/2018 07:10 AM, Jia-Ju Bai wrote:
> dn_route_init() is never called in atomic context.
>
> The call chain ending up at dn_route_init() is:
> [1] dn_route_init() <- decnet_init()
> decnet_init() is only set as a parameter of module_init().
>
> Despite never getting called from atomic context,
> dn_route_init() calls __get_free_pages() with GFP_ATOMIC,
> which waits busily for allocation.
> GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
> to avoid busy waiting and improve the possibility of sucessful allocation.
>
> This is found by a static analysis tool named DCNS written by myself.
> And I also manually check it.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> ---
> net/decnet/dn_route.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
> index 0bd3afd..59ed12a 100644
> --- a/net/decnet/dn_route.c
> +++ b/net/decnet/dn_route.c
> @@ -1898,7 +1898,7 @@ void __init dn_route_init(void)
> while(dn_rt_hash_mask & (dn_rt_hash_mask - 1))
> dn_rt_hash_mask--;
> dn_rt_hash_table = (struct dn_rt_hash_bucket *)
> - __get_free_pages(GFP_ATOMIC, order);
> + __get_free_pages(GFP_KERNEL, order);
> } while (dn_rt_hash_table == NULL && --order > 0);
>
> if (!dn_rt_hash_table)
>
This might OOM under pressure.
This would need __GFP_NOWARN | __GFP_NORETRY I guess, and would target net-next
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] net: decnet: Replace GFP_ATOMIC with GFP_KERNEL in dn_route_init
2018-04-09 14:44 ` Eric Dumazet
@ 2018-04-09 14:48 ` Jia-Ju Bai
0 siblings, 0 replies; 3+ messages in thread
From: Jia-Ju Bai @ 2018-04-09 14:48 UTC (permalink / raw)
To: Eric Dumazet, davem, kafai, weiwan, dsa, johannes.berg, fw
Cc: linux-decnet-user, netdev, linux-kernel
On 2018/4/9 22:44, Eric Dumazet wrote:
>
> On 04/09/2018 07:10 AM, Jia-Ju Bai wrote:
>> dn_route_init() is never called in atomic context.
>>
>> The call chain ending up at dn_route_init() is:
>> [1] dn_route_init() <- decnet_init()
>> decnet_init() is only set as a parameter of module_init().
>>
>> Despite never getting called from atomic context,
>> dn_route_init() calls __get_free_pages() with GFP_ATOMIC,
>> which waits busily for allocation.
>> GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
>> to avoid busy waiting and improve the possibility of sucessful allocation.
>>
>> This is found by a static analysis tool named DCNS written by myself.
>> And I also manually check it.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
>> ---
>> net/decnet/dn_route.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
>> index 0bd3afd..59ed12a 100644
>> --- a/net/decnet/dn_route.c
>> +++ b/net/decnet/dn_route.c
>> @@ -1898,7 +1898,7 @@ void __init dn_route_init(void)
>> while(dn_rt_hash_mask & (dn_rt_hash_mask - 1))
>> dn_rt_hash_mask--;
>> dn_rt_hash_table = (struct dn_rt_hash_bucket *)
>> - __get_free_pages(GFP_ATOMIC, order);
>> + __get_free_pages(GFP_KERNEL, order);
>> } while (dn_rt_hash_table == NULL && --order > 0);
>>
>> if (!dn_rt_hash_table)
>>
> This might OOM under pressure.
Sorry, I do not understand this.
Could you please explain the reason?
> This would need __GFP_NOWARN | __GFP_NORETRY I guess, and would target net-next
>
Do you mean
__get_free_pages(__GFP_NOWARN | __GFP_NORETRY) or
__get_free_pages(__GFP_NOWARN | __GFP_NORETRY | GFP_KERNEL)?
Best wishes,
Jia-Ju Bai
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-04-09 14:10 [PATCH] net: decnet: Replace GFP_ATOMIC with GFP_KERNEL in dn_route_init Jia-Ju Bai
2018-04-09 14:44 ` Eric Dumazet
2018-04-09 14:48 ` Jia-Ju Bai
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