From: Dave Kleikamp <dave.kleikamp@oracle.com>
To: Julian Calaby <julian.calaby@gmail.com>,
Sowmini Varadhan <sowmini.varadhan@oracle.com>
Cc: "David S. Miller" <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>,
sparclinux <sparclinux@vger.kernel.org>
Subject: Re: [PATCHv4 3/4] sparc64: Avoid irqsave/restore on vio.lock if in_softirq()
Date: Tue, 21 Oct 2014 18:56:01 -0500 [thread overview]
Message-ID: <5446F291.1030400@oracle.com> (raw)
In-Reply-To: <CAGRGNgXvKJBhOE1z3=_gZkE=X94HnoAvTN6Zv5G1h8JuFfS8Ng@mail.gmail.com>
On 10/21/2014 05:35 PM, Julian Calaby wrote:
> Hi Sowmini,
>
> On Wed, Oct 22, 2014 at 1:16 AM, Sowmini Varadhan
> <sowmini.varadhan@oracle.com> wrote:
>> For NAPIfied drivers , there is no need to
>> synchronize by doing irqsave/restore on vio.lock in the I/O
>> path.
>>
>> Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
>> ---
>> arch/sparc/kernel/viohs.c | 8 +++++---
>> 1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/sparc/kernel/viohs.c b/arch/sparc/kernel/viohs.c
>> index 7ef081a..d731586 100644
>> --- a/arch/sparc/kernel/viohs.c
>> +++ b/arch/sparc/kernel/viohs.c
>> @@ -747,10 +747,11 @@ EXPORT_SYMBOL(vio_ldc_free);
>>
>> void vio_port_up(struct vio_driver_state *vio)
>> {
>> - unsigned long flags;
>> + unsigned long flags = 0;
>
> Is gcc not smart enough to know that this variable isn't used before
> it's set? (I assume it isn't used elsewhere in this function)
It probably assumes in_softirq() might evaluate differently in the each
case.
>
>> int err, state;
>>
>> - spin_lock_irqsave(&vio->lock, flags);
>> + if (!in_softirq())
>> + spin_lock_irqsave(&vio->lock, flags);
>>
>> state = ldc_state(vio->lp);
>>
>> @@ -777,7 +778,8 @@ void vio_port_up(struct vio_driver_state *vio)
>> mod_timer(&vio->timer, expires);
>> }
>>
>> - spin_unlock_irqrestore(&vio->lock, flags);
>> + if (!in_softirq())
>> + spin_unlock_irqrestore(&vio->lock, flags);
>> }
>> EXPORT_SYMBOL(vio_port_up);
>
> Thanks,
>
next prev parent reply other threads:[~2014-10-21 23:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-21 14:16 [PATCHv4 3/4] sparc64: Avoid irqsave/restore on vio.lock if in_softirq() Sowmini Varadhan
2014-10-21 22:35 ` Julian Calaby
2014-10-21 22:39 ` Sowmini Varadhan
2014-10-21 22:42 ` Julian Calaby
2014-10-21 23:56 ` Dave Kleikamp [this message]
2014-10-22 0:16 ` Sowmini Varadhan
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=5446F291.1030400@oracle.com \
--to=dave.kleikamp@oracle.com \
--cc=davem@davemloft.net \
--cc=julian.calaby@gmail.com \
--cc=netdev@vger.kernel.org \
--cc=sowmini.varadhan@oracle.com \
--cc=sparclinux@vger.kernel.org \
/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).