* ndo_get_stats and rtnl_netlink
@ 2012-09-09 15:23 Shlomo Pongartz
2012-09-10 9:09 ` Eric Dumazet
0 siblings, 1 reply; 4+ messages in thread
From: Shlomo Pongartz @ 2012-09-09 15:23 UTC (permalink / raw)
To: netdev
Hi,
Just realized that dev_get_stats which calls into a netdevice
ndo_get_stats64/ndo_get_stats can be
called with or without RTNL lock protection. If called from
rtnl_fill_ifinfo e.g as of invocation of
"ip link show <interface>, there IS locking, however if called from
dev_seq_printf_stats e.g as of
invocation of reading the /sys/class/net/<interface>/statistics/
entries, etc more cases -- no locking.
This turned to be problematic when implementing the ethtool
"set_channels" directive which
changes the number of **rings**, since we stepped on a bug where the
rings data structure was
changed by the ethtool flow in the same time a statistics call was done
into the driver, etc.
What would be the way to continue here, per driver lock sounds non
generic...
Regards
Shlomo Pongratz
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: ndo_get_stats and rtnl_netlink
2012-09-09 15:23 ndo_get_stats and rtnl_netlink Shlomo Pongartz
@ 2012-09-10 9:09 ` Eric Dumazet
2012-09-10 19:10 ` Or Gerlitz
0 siblings, 1 reply; 4+ messages in thread
From: Eric Dumazet @ 2012-09-10 9:09 UTC (permalink / raw)
To: Shlomo Pongartz; +Cc: netdev
On Sun, 2012-09-09 at 18:23 +0300, Shlomo Pongartz wrote:
> Hi,
>
> Just realized that dev_get_stats which calls into a netdevice
> ndo_get_stats64/ndo_get_stats can be
> called with or without RTNL lock protection. If called from
> rtnl_fill_ifinfo e.g as of invocation of
> "ip link show <interface>, there IS locking, however if called from
> dev_seq_printf_stats e.g as of
> invocation of reading the /sys/class/net/<interface>/statistics/
> entries, etc more cases -- no locking.
>
> This turned to be problematic when implementing the ethtool
> "set_channels" directive which
> changes the number of **rings**, since we stepped on a bug where the
> rings data structure was
> changed by the ethtool flow in the same time a statistics call was done
> into the driver, etc.
>
> What would be the way to continue here, per driver lock sounds non
> generic...
RTNL locking is not needed to fetch stats, and would be overkill.
Each driver has its own way to protect/gather its stats.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: ndo_get_stats and rtnl_netlink
2012-09-10 9:09 ` Eric Dumazet
@ 2012-09-10 19:10 ` Or Gerlitz
2012-09-10 19:15 ` Eric Dumazet
0 siblings, 1 reply; 4+ messages in thread
From: Or Gerlitz @ 2012-09-10 19:10 UTC (permalink / raw)
To: Eric Dumazet; +Cc: Shlomo Pongartz, netdev
On Mon, Sep 10, 2012 at 12:09 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> RTNL locking is not needed to fetch stats, and would be overkill.
> Each driver has its own way to protect/gather its stats.
FWIW, again, when dev_get_stats is called from rtnl_fill_ifinfo e.g as
of invocation
of "ip link show <interface>, there IS RTNL locking, is that a problem?
Or.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: ndo_get_stats and rtnl_netlink
2012-09-10 19:10 ` Or Gerlitz
@ 2012-09-10 19:15 ` Eric Dumazet
0 siblings, 0 replies; 4+ messages in thread
From: Eric Dumazet @ 2012-09-10 19:15 UTC (permalink / raw)
To: Or Gerlitz; +Cc: Shlomo Pongartz, netdev
On Mon, 2012-09-10 at 22:10 +0300, Or Gerlitz wrote:
> On Mon, Sep 10, 2012 at 12:09 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
> > RTNL locking is not needed to fetch stats, and would be overkill.
> > Each driver has its own way to protect/gather its stats.
>
> FWIW, again, when dev_get_stats is called from rtnl_fill_ifinfo e.g as
> of invocation
> of "ip link show <interface>, there IS RTNL locking, is that a problem?
>
> Or.
Why should it be a problem ?
A dev_get_stats() is not allowed to sleep, so its not allowed to use
RTNL by itself.
So caller might use RTNL, we dont care at all.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2012-09-10 19:15 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2012-09-09 15:23 ndo_get_stats and rtnl_netlink Shlomo Pongartz
2012-09-10 9:09 ` Eric Dumazet
2012-09-10 19:10 ` Or Gerlitz
2012-09-10 19:15 ` Eric Dumazet
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