From: Xianting Tian <xianting.tian@linux.alibaba.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: arei.gonglei@huawei.com, mst@redhat.com, jasowang@redhat.com,
xuanzhuo@linux.alibaba.com, herbert@gondor.apana.org.au,
davem@davemloft.net, amit@kernel.org, arnd@arndb.de,
marcel@holtmann.org, johan.hedberg@gmail.com,
luiz.dentz@gmail.com, linux-bluetooth@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
Xianting Tian <tianxianting.txt@alibaba-inc.com>
Subject: Re: [PATCH 1/3] virtio-crypto: fixup potential cpu stall when free unused bufs
Date: Fri, 9 Jun 2023 21:49:39 +0800 [thread overview]
Message-ID: <91aa6ce0-e8a3-21ac-d29e-b2a47f6386d1@linux.alibaba.com> (raw)
In-Reply-To: <2023060940-wrongdoer-wince-5701@gregkh>
在 2023/6/9 下午9:41, Greg KH 写道:
> On Fri, Jun 09, 2023 at 03:39:24PM +0200, Greg KH wrote:
>> On Fri, Jun 09, 2023 at 09:18:15PM +0800, Xianting Tian wrote:
>>> From: Xianting Tian <tianxianting.txt@alibaba-inc.com>
>>>
>>> Cpu stall issue may happen if device is configured with multi queues
>>> and large queue depth, so fix it.
>>>
>>> Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>
>>> ---
>>> drivers/crypto/virtio/virtio_crypto_core.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/crypto/virtio/virtio_crypto_core.c b/drivers/crypto/virtio/virtio_crypto_core.c
>>> index 1198bd306365..94849fa3bd74 100644
>>> --- a/drivers/crypto/virtio/virtio_crypto_core.c
>>> +++ b/drivers/crypto/virtio/virtio_crypto_core.c
>>> @@ -480,6 +480,7 @@ static void virtcrypto_free_unused_reqs(struct virtio_crypto *vcrypto)
>>> kfree(vc_req->req_data);
>>> kfree(vc_req->sgs);
>>> }
>>> + cond_resched();
>> that's not "fixing a stall", it is "call the scheduler because we are
>> taking too long". The CPU isn't stalled at all, just busy.
>>
>> Are you sure this isn't just a bug in the code? Why is this code taking
>> so long that you have to force the scheduler to run? This is almost
>> always a sign that something else needs to be fixed instead.
> And same comment on the other 2 patches, please fix this properly.
>
> Also, this is a tight loop that is just freeing memory, why is it taking
> so long? Why do you want it to take longer (which is what you are doing
> here), ideally it would be faster, not slower, so you are now slowing
> down the system overall with this patchset, right?
yes, it is the similar fix with one for virtio-net
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/net/virtio_net.c?h=v6.4-rc5&id=f8bb5104394560e29017c25bcade4c6b7aabd108
<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/net/virtio_net.c?h=v6.4-rc5&id=f8bb5104394560e29017c25bcade4c6b7aabd108>
>
> thanks,
>
> greg k-h
next prev parent reply other threads:[~2023-06-09 13:50 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 13:18 [PATCH 0/3] fixup potential cpu stall Xianting Tian
2023-06-09 13:18 ` [PATCH 1/3] virtio-crypto: fixup potential cpu stall when free unused bufs Xianting Tian
2023-06-09 13:39 ` Greg KH
2023-06-09 13:41 ` Greg KH
2023-06-09 13:49 ` Xianting Tian [this message]
2023-06-09 14:05 ` Greg KH
2023-06-09 14:25 ` Xianting Tian
2023-06-09 16:02 ` Michael S. Tsirkin
2023-06-09 15:57 ` Michael S. Tsirkin
2023-06-10 3:20 ` Xianting Tian
2023-06-10 6:51 ` Greg KH
2023-06-09 15:58 ` Michael S. Tsirkin
2023-06-09 13:18 ` [PATCH 2/3] virtio_console: " Xianting Tian
2023-06-09 16:05 ` Michael S. Tsirkin
2023-06-10 3:19 ` Xianting Tian
2023-06-09 13:18 ` [PATCH 3/3] virtio_bt: " Xianting Tian
2023-06-22 11:59 ` [PATCH 0/3] fixup potential cpu stall Michael S. Tsirkin
2023-06-23 0:58 ` Xianting Tian
2023-07-06 20:10 ` patchwork-bot+bluetooth
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