linux-kernel - Re: [PATCH bpf-next 1/4] bpf: enable task local storage for tracing programs

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Date:   Mon, 11 Jan 2021 23:41:26 +0000
From:   Song Liu <songliubraving@...com>
To:     Martin Lau <kafai@...com>
CC:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "andrii@...nel.org" <andrii@...nel.org>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "kpsingh@...omium.org" <kpsingh@...omium.org>,
        Kernel Team <Kernel-team@...com>,
        "haoluo@...gle.com" <haoluo@...gle.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH bpf-next 1/4] bpf: enable task local storage for tracing
 programs



> On Jan 11, 2021, at 10:56 AM, Martin Lau <kafai@...com> wrote:
> 
> On Fri, Jan 08, 2021 at 03:19:47PM -0800, Song Liu wrote:
> 
> [ ... ]
> 
>> diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
>> index dd5aedee99e73..9bd47ad2b26f1 100644
>> --- a/kernel/bpf/bpf_local_storage.c
>> +++ b/kernel/bpf/bpf_local_storage.c
>> @@ -140,17 +140,18 @@ static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
>> {
>> 	struct bpf_local_storage *local_storage;
>> 	bool free_local_storage = false;
>> +	unsigned long flags;
>> 
>> 	if (unlikely(!selem_linked_to_storage(selem)))
>> 		/* selem has already been unlinked from sk */
>> 		return;
>> 
>> 	local_storage = rcu_dereference(selem->local_storage);
>> -	raw_spin_lock_bh(&local_storage->lock);
>> +	raw_spin_lock_irqsave(&local_storage->lock, flags);
> It will be useful to have a few words in commit message on this change
> for future reference purpose.
> 
> Please also remove the in_irq() check from bpf_sk_storage.c
> to avoid confusion in the future.  It probably should
> be in a separate patch.

Do you mean we allow bpf_sk_storage_get_tracing() and 
bpf_sk_storage_delete_tracing() in irq context? Like

diff --git i/net/core/bpf_sk_storage.c w/net/core/bpf_sk_storage.c
index 4edd033e899c0..14dd5e3c67402 100644
--- i/net/core/bpf_sk_storage.c
+++ w/net/core/bpf_sk_storage.c
@@ -425,7 +425,7 @@ BPF_CALL_4(bpf_sk_storage_get_tracing, struct bpf_map *, map, struct sock *, sk,
 BPF_CALL_2(bpf_sk_storage_delete_tracing, struct bpf_map *, map,
           struct sock *, sk)
 {
-       if (in_irq() || in_nmi())
+       if (in_nmi())
                return -EPERM;

        return ____bpf_sk_storage_delete(map, sk);

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