From: Anton Ivanov <anton.ivanov@cambridgegreys.com>
To: Richard Weinberger <richard@nod.at>
Cc: Song Liu <songliubraving@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>,
linux-um <linux-um@lists.infradead.org>,
Jeff Dike <jdike@addtoit.com>,
kernel-janitors <kernel-janitors@vger.kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Wei Yongjun <weiyongjun1@huawei.com>,
netdev <netdev@vger.kernel.org>,
bpf@vger.kernel.org, Martin KaFai Lau <kafai@fb.com>,
Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [PATCH -next] um: vector: use GFP_ATOMIC under spin lock
Date: Thu, 28 Nov 2019 09:24:12 +0000 [thread overview]
Message-ID: <ceedf42c-2dc0-df2e-cf3f-323c675dec78@cambridgegreys.com> (raw)
In-Reply-To: <1784077834.99875.1574930472125.JavaMail.zimbra@nod.at>
On 28/11/2019 08:41, Richard Weinberger wrote:
> ----- Ursprüngliche Mail -----
>> Von: "anton ivanov" <anton.ivanov@cambridgegreys.com>
>> An: "Dan Carpenter" <dan.carpenter@oracle.com>, "Wei Yongjun" <weiyongjun1@huawei.com>
>> CC: "Song Liu" <songliubraving@fb.com>, "Daniel Borkmann" <daniel@iogearbox.net>, "kernel-janitors"
>> <kernel-janitors@vger.kernel.org>, "richard" <richard@nod.at>, "Jeff Dike" <jdike@addtoit.com>, "linux-um"
>> <linux-um@lists.infradead.org>, "Alexei Starovoitov" <ast@kernel.org>, "netdev" <netdev@vger.kernel.org>,
>> bpf@vger.kernel.org, "Martin KaFai Lau" <kafai@fb.com>
>> Gesendet: Donnerstag, 28. November 2019 09:18:30
>> Betreff: Re: [PATCH -next] um: vector: use GFP_ATOMIC under spin lock
>
>> On 28/11/2019 08:06, Dan Carpenter wrote:
>>> On Thu, Nov 28, 2019 at 02:01:47AM +0000, Wei Yongjun wrote:
>>>> A spin lock is taken here so we should use GFP_ATOMIC.
>>>>
>>>> Fixes: 9807019a62dc ("um: Loadable BPF "Firmware" for vector drivers")
>>>> Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
>>>> ---
>>>> arch/um/drivers/vector_kern.c | 4 ++--
>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/arch/um/drivers/vector_kern.c b/arch/um/drivers/vector_kern.c
>>>> index 92617e16829e..6ff0065a271d 100644
>>>> --- a/arch/um/drivers/vector_kern.c
>>>> +++ b/arch/um/drivers/vector_kern.c
>>>> @@ -1402,7 +1402,7 @@ static int vector_net_load_bpf_flash(struct net_device
>>>> *dev,
>>>> kfree(vp->bpf->filter);
>>>> vp->bpf->filter = NULL;
>>>> } else {
>>>> - vp->bpf = kmalloc(sizeof(struct sock_fprog), GFP_KERNEL);
>>>> + vp->bpf = kmalloc(sizeof(struct sock_fprog), GFP_ATOMIC);
>>>> if (vp->bpf == NULL) {
>>>> netdev_err(dev, "failed to allocate memory for firmware\n");
>>>> goto flash_fail;
>>>> @@ -1414,7 +1414,7 @@ static int vector_net_load_bpf_flash(struct net_device
>>>> *dev,
>>>> if (request_firmware(&fw, efl->data, &vdevice->pdev.dev))
>>> ^^^^^^^^^^^^^^^^
>>>
>>> Is it really possible to call request_firmware() while holding a
>>> spin_lock? I was so sure that read from the disk.
>>
>> Works, I tested the patch quite a few times.
>
> It works because of the nature of UML ->no SMP or PREEMPT.
> But better request the firmware before taking the spinlock.
> request_firmware() can block.
> Same for the kmalloc(), just allocate the buffer before and then assign
> the pointer under the lock. That way you don't need GFP_ATOMIC.
Ack.
I will make an incremental on top of the existing patch (as that is
already in -next
Brgds,
>
> Thanks,
> //richard
>
> _______________________________________________
> linux-um mailing list
> linux-um@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-um
>
--
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/
prev parent reply other threads:[~2019-11-28 9:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-28 2:01 [PATCH -next] um: vector: use GFP_ATOMIC under spin lock Wei Yongjun
2019-11-28 7:51 ` Anton Ivanov
2019-11-28 8:06 ` Dan Carpenter
2019-11-28 8:18 ` Anton Ivanov
2019-11-28 8:37 ` Dan Carpenter
2019-11-28 9:22 ` Anton Ivanov
2019-11-28 8:41 ` Richard Weinberger
2019-11-28 9:24 ` Anton Ivanov [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ceedf42c-2dc0-df2e-cf3f-323c675dec78@cambridgegreys.com \
--to=anton.ivanov@cambridgegreys.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=dan.carpenter@oracle.com \
--cc=daniel@iogearbox.net \
--cc=jdike@addtoit.com \
--cc=kafai@fb.com \
--cc=kernel-janitors@vger.kernel.org \
--cc=linux-um@lists.infradead.org \
--cc=netdev@vger.kernel.org \
--cc=richard@nod.at \
--cc=songliubraving@fb.com \
--cc=weiyongjun1@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).