Re: [PATCH v2] net: tipc: Replace GFP_ATOMIC with GFP_KERNEL in tipc_mon_create

[Ying Xue]

On 04/10/2018 09:17 AM, Jia-Ju Bai wrote:
> tipc_mon_create() is never called in atomic context.
> 
> The call chain ending up at dn_route_init() is:

Sorry, I don't think there is any relationship between the following
call chain with dn_route_init().

> [1] tipc_mon_create() <- tipc_enable_bearer() <- tipc_nl_bearer_enable()
> tipc_nl_bearer_enable() calls rtnl_lock(), which indicates this function
> is not called in atomic context.
> 
> Despite never getting called from atomic context,
> tipc_mon_create() calls kzalloc() with GFP_ATOMIC,
> which does not sleep for allocation.
> GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
> which can sleep and improve the possibility of sucessful allocation.

s/sucessful/successful

> 
> 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 > ---
> v2:
> * Modify the description of GFP_ATOMIC in v1.
>   Thank Eric for good advice.
> ---
>  net/tipc/monitor.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/net/tipc/monitor.c b/net/tipc/monitor.c
> index 9e109bb..9714d80 100644
> --- a/net/tipc/monitor.c
> +++ b/net/tipc/monitor.c
> @@ -604,9 +604,9 @@ int tipc_mon_create(struct net *net, int bearer_id)
>   if (tn->monitors[bearer_id])
>   return 0;
>  
> - mon = kzalloc(sizeof(*mon), GFP_ATOMIC);
> - self = kzalloc(sizeof(*self), GFP_ATOMIC);
> - dom = kzalloc(sizeof(*dom), GFP_ATOMIC);
> + mon = kzalloc(sizeof(*mon), GFP_KERNEL);
> + self = kzalloc(sizeof(*self), GFP_KERNEL);
> + dom = kzalloc(sizeof(*dom), GFP_KERNEL);
>   if (!mon || !self || !dom) {
>   kfree(mon);
>   kfree(self);
> 

Re: [PATCH v2] net: tipc: Replace GFP_ATOMIC with GFP_KERNEL in tipc_mon_create

[Jia-Ju Bai]

On 2018/4/11 18:11, Ying Xue wrote:

On 04/10/2018 09:17 AM, Jia-Ju Bai wrote:

tipc_mon_create() is never called in atomic context.

The call chain ending up at dn_route_init() is:

Sorry, I don't think there is any relationship between the following
call chain with dn_route_init().


[1] tipc_mon_create() <- tipc_enable_bearer() <- tipc_nl_bearer_enable()
tipc_nl_bearer_enable() calls rtnl_lock(), which indicates this function
is not called in atomic context.

Despite never getting called from atomic context,
tipc_mon_create() calls kzalloc() with GFP_ATOMIC,
which does not sleep for allocation.
GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
which can sleep and improve the possibility of sucessful allocation.

s/sucessful/successful


Thanks for your reply.
I am sorry for my mistakes.
I will revised the text and send a V3.


Jia-Ju Bai