| Message ID | 20220202122848.647635-3-bigeasy@linutronix.de (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | net: dev: PREEMPT_RT fixups. | expand |
On Wed, Feb 2, 2022 at 4:28 AM Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote: > > The get_cpu() usage was added in commit > b0e28f1effd1d ("net: netif_rx() must disable preemption") > > because ip_dev_loopback_xmit() invoked netif_rx() with enabled preemtion > causing a warning in smp_processor_id(). The function netif_rx() should > only be invoked from an interrupt context which implies disabled > preemption. The commit > e30b38c298b55 ("ip: Fix ip_dev_loopback_xmit()") > > was addressing this and replaced netif_rx() with in netif_rx_ni() in > ip_dev_loopback_xmit(). > > Based on the discussion on the list, the former patch (b0e28f1effd1d) > should not have been applied only the latter (e30b38c298b55). > > Remove get_cpu() since the function is supossed to be invoked from > context with stable per-CPU pointers (either by disabling preemption or > software interrupts). > > Link: https://lkml.kernel.org/r/20100415.013347.98375530.davem@davemloft.net > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > --- Reviewed-by: Eric Dumazet <edumazet@google.com> Thanks !
Sebastian Andrzej Siewior <bigeasy@linutronix.de> writes: > The get_cpu() usage was added in commit > b0e28f1effd1d ("net: netif_rx() must disable preemption") > > because ip_dev_loopback_xmit() invoked netif_rx() with enabled preemtion > causing a warning in smp_processor_id(). The function netif_rx() should > only be invoked from an interrupt context which implies disabled > preemption. The commit > e30b38c298b55 ("ip: Fix ip_dev_loopback_xmit()") > > was addressing this and replaced netif_rx() with in netif_rx_ni() in > ip_dev_loopback_xmit(). > > Based on the discussion on the list, the former patch (b0e28f1effd1d) > should not have been applied only the latter (e30b38c298b55). > > Remove get_cpu() since the function is supossed to be invoked from > context with stable per-CPU pointers (either by disabling preemption or > software interrupts). > > Link: https://lkml.kernel.org/r/20100415.013347.98375530.davem@davemloft.net > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
diff --git a/net/core/dev.c b/net/core/dev.c index 325b70074f4ae..0d13340ed4054 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4810,8 +4810,7 @@ static int netif_rx_internal(struct sk_buff *skb) { unsigned int qtail; - ret = enqueue_to_backlog(skb, get_cpu(), &qtail); - put_cpu(); + ret = enqueue_to_backlog(skb, smp_processor_id(), &qtail); } return ret; }
The get_cpu() usage was added in commit b0e28f1effd1d ("net: netif_rx() must disable preemption") because ip_dev_loopback_xmit() invoked netif_rx() with enabled preemtion causing a warning in smp_processor_id(). The function netif_rx() should only be invoked from an interrupt context which implies disabled preemption. The commit e30b38c298b55 ("ip: Fix ip_dev_loopback_xmit()") was addressing this and replaced netif_rx() with in netif_rx_ni() in ip_dev_loopback_xmit(). Based on the discussion on the list, the former patch (b0e28f1effd1d) should not have been applied only the latter (e30b38c298b55). Remove get_cpu() since the function is supossed to be invoked from context with stable per-CPU pointers (either by disabling preemption or software interrupts). Link: https://lkml.kernel.org/r/20100415.013347.98375530.davem@davemloft.net Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- net/core/dev.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)