| Message ID | 20220825113645.212996-2-bigeasy@linutronix.de (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 3f8ae9fe0409698799e173f698b714f34570b64b |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | net: u64_stats fixups for 32bit. | expand |
On Thu, Aug 25, 2022 at 6:36 AM Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote: > > xrs700x_read_port_counters() updates the stats from a worker using the > u64_stats_update_begin() version. This is okay on 32-UP since on the > reader side preemption is disabled. > On 32bit-SMP the writer can be preempted by the reader at which point > the reader will spin on the seqcount until writer continues and > completes the update. > > Assigning the mib_mutex mutex to the underlying seqcount would ensure > proper synchronisation. The API for that on the u64_stats_init() side > isn't available. Since it is the only user, just use disable interrupts > during the update. > > Use u64_stats_update_begin_irqsave() on the writer side to ensure an > uninterrupted update. > > Fixes: ee00b24f32eb8 ("net: dsa: add Arrow SpeedChips XRS700x driver") > Cc: Andrew Lunn <andrew@lunn.ch> > Cc: Florian Fainelli <f.fainelli@gmail.com> > Cc: George McCollister <george.mccollister@gmail.com> > Cc: Vivien Didelot <vivien.didelot@gmail.com> > Cc: Vladimir Oltean <olteanv@gmail.com> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > --- > drivers/net/dsa/xrs700x/xrs700x.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/dsa/xrs700x/xrs700x.c b/drivers/net/dsa/xrs700x/xrs700x.c > index 3887ed33c5fe2..fa622639d6401 100644 > --- a/drivers/net/dsa/xrs700x/xrs700x.c > +++ b/drivers/net/dsa/xrs700x/xrs700x.c > @@ -109,6 +109,7 @@ static void xrs700x_read_port_counters(struct xrs700x *priv, int port) > { > struct xrs700x_port *p = &priv->ports[port]; > struct rtnl_link_stats64 stats; > + unsigned long flags; > int i; > > memset(&stats, 0, sizeof(stats)); > @@ -138,9 +139,9 @@ static void xrs700x_read_port_counters(struct xrs700x *priv, int port) > */ > stats.rx_packets += stats.multicast; > > - u64_stats_update_begin(&p->syncp); > + flags = u64_stats_update_begin_irqsave(&p->syncp); > p->stats64 = stats; > - u64_stats_update_end(&p->syncp); > + u64_stats_update_end_irqrestore(&p->syncp, flags); > > mutex_unlock(&p->mib_mutex); > } > -- > 2.37.2 > Acked-by: George McCollister <george.mccollister@gmail.com> Thanks, George
diff --git a/drivers/net/dsa/xrs700x/xrs700x.c b/drivers/net/dsa/xrs700x/xrs700x.c index 3887ed33c5fe2..fa622639d6401 100644 --- a/drivers/net/dsa/xrs700x/xrs700x.c +++ b/drivers/net/dsa/xrs700x/xrs700x.c @@ -109,6 +109,7 @@ static void xrs700x_read_port_counters(struct xrs700x *priv, int port) { struct xrs700x_port *p = &priv->ports[port]; struct rtnl_link_stats64 stats; + unsigned long flags; int i; memset(&stats, 0, sizeof(stats)); @@ -138,9 +139,9 @@ static void xrs700x_read_port_counters(struct xrs700x *priv, int port) */ stats.rx_packets += stats.multicast; - u64_stats_update_begin(&p->syncp); + flags = u64_stats_update_begin_irqsave(&p->syncp); p->stats64 = stats; - u64_stats_update_end(&p->syncp); + u64_stats_update_end_irqrestore(&p->syncp, flags); mutex_unlock(&p->mib_mutex); }
xrs700x_read_port_counters() updates the stats from a worker using the u64_stats_update_begin() version. This is okay on 32-UP since on the reader side preemption is disabled. On 32bit-SMP the writer can be preempted by the reader at which point the reader will spin on the seqcount until writer continues and completes the update. Assigning the mib_mutex mutex to the underlying seqcount would ensure proper synchronisation. The API for that on the u64_stats_init() side isn't available. Since it is the only user, just use disable interrupts during the update. Use u64_stats_update_begin_irqsave() on the writer side to ensure an uninterrupted update. Fixes: ee00b24f32eb8 ("net: dsa: add Arrow SpeedChips XRS700x driver") Cc: Andrew Lunn <andrew@lunn.ch> Cc: Florian Fainelli <f.fainelli@gmail.com> Cc: George McCollister <george.mccollister@gmail.com> Cc: Vivien Didelot <vivien.didelot@gmail.com> Cc: Vladimir Oltean <olteanv@gmail.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- drivers/net/dsa/xrs700x/xrs700x.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)