linux-kernel - Re: [PATCH trival 1/2] bpf: clean up put_cpu

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Date:   Tue, 27 Sep 2016 12:52:38 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Shaohua Li <shli@...com>
CC:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        Tejun Heo <tj@...nel.org>, Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH trival 1/2] bpf: clean up put_cpu_var usage

Shaohua,

On 09/27/2016 01:51 AM, Alexei Starovoitov wrote:
> On Mon, Sep 26, 2016 at 11:14:50AM -0700, Shaohua Li wrote:
>> put_cpu_var takes the percpu data, not the data returned from
>> get_cpu_var.
>>
>> This doesn't change the behavior.
>>
>> Cc: Tejun Heo <tj@...nel.org>
>> Cc: Alexei Starovoitov <ast@...nel.org>
>> Signed-off-by: Shaohua Li <shli@...com>
>
> Looks good. Nice catch.
> Please rebase to net-next tree and send it to netdev list.

+1

> Otherwise we'll have conflicts at the time of the merge window.

While you're at it, the same kind of cleanup can be done for
prandom_u32() and prandom_bytes(), so you could either squash
that into this patch as well or make it two patches. Both for
netdev.

Thanks,
Daniel

>> ---
>>   kernel/bpf/core.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
>> index 03fd23d..b73913b 100644
>> --- a/kernel/bpf/core.c
>> +++ b/kernel/bpf/core.c
>> @@ -1031,7 +1031,7 @@ u64 bpf_user_rnd_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
>>
>>   	state = &get_cpu_var(bpf_user_rnd_state);
>>   	res = prandom_u32_state(state);
>> -	put_cpu_var(state);
>> +	put_cpu_var(bpf_user_rnd_state);
>>
>>   	return res;
>>   }
>> --
>> 2.9.3
>>