On Sat, Sep 30, 2023 at 01:59:53PM +0200, Eric Dumazet wrote:
> On Fri, Sep 22, 2023 at 1:13 PM Christian Marangi <ansuelsmth@xxxxxxxxx> wrote:
> >
> > We currently have napi_if_scheduled_mark_missed that can be used to
> > check if napi is scheduled but that does more thing than simply checking
> > it and return a bool. Some driver already implement custom function to
> > check if napi is scheduled.
> >
> > Drop these custom function and introduce napi_is_scheduled that simply
> > check if napi is scheduled atomically.
> >
> > Update any driver and code that implement a similar check and instead
> > use this new helper.
> >
> > Signed-off-by: Christian Marangi <ansuelsmth@xxxxxxxxx>
> > ---
> > drivers/net/ethernet/chelsio/cxgb3/sge.c | 8 --------
> > drivers/net/wireless/realtek/rtw89/core.c | 2 +-
> > include/linux/netdevice.h | 5 +++++
> > net/core/dev.c | 2 +-
> > 4 files changed, 7 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/chelsio/cxgb3/sge.c b/drivers/net/ethernet/chelsio/cxgb3/sge.c
> > index 2e9a74fe0970..71fa2dc19034 100644
> > --- a/drivers/net/ethernet/chelsio/cxgb3/sge.c
> > +++ b/drivers/net/ethernet/chelsio/cxgb3/sge.c
> > @@ -2501,14 +2501,6 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
> > return work_done;
> > }
> >
> > -/*
> > - * Returns true if the device is already scheduled for polling.
> > - */
> > -static inline int napi_is_scheduled(struct napi_struct *napi)
> > -{
> > - return test_bit(NAPI_STATE_SCHED, &napi->state);
> > -}
> > -
> > /**
> > * process_pure_responses - process pure responses from a response queue
> > * @adap: the adapter
> > diff --git a/drivers/net/wireless/realtek/rtw89/core.c b/drivers/net/wireless/realtek/rtw89/core.c
> > index 133bf289bacb..bbf4ea3639d4 100644
> > --- a/drivers/net/wireless/realtek/rtw89/core.c
> > +++ b/drivers/net/wireless/realtek/rtw89/core.c
> > @@ -1744,7 +1744,7 @@ static void rtw89_core_rx_to_mac80211(struct rtw89_dev *rtwdev,
> > struct napi_struct *napi = &rtwdev->napi;
> >
> > /* In low power mode, napi isn't scheduled. Receive it to netif. */
> > - if (unlikely(!test_bit(NAPI_STATE_SCHED, &napi->state)))
> > + if (unlikely(!napi_is_scheduled(napi)))
> > napi = NULL;
> >
> > rtw89_core_hw_to_sband_rate(rx_status);
> > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > index db3d8429d50d..8eac00cd3b92 100644
> > --- a/include/linux/netdevice.h
> > +++ b/include/linux/netdevice.h
> > @@ -482,6 +482,11 @@ static inline bool napi_prefer_busy_poll(struct napi_struct *n)
> > return test_bit(NAPI_STATE_PREFER_BUSY_POLL, &n->state);
> > }
> >
>
>
> In which context is it safe to call this helper ?
>
test_bit is atomic so it should be always safe. Also the idea of this
check (and from what I can see this apply also to the other 2 user) is
somehow best effort, we check if in the current istant there is a napi
scheduled and we act.
> I fear that making this available will add more bugs.
>
> For instance rspq_check_napi() seems buggy to me.
>
Mhhh why? Am I opening a can of worms?
> > +static inline bool napi_is_scheduled(struct napi_struct *n)
>
> const ...
>
Will change in v2. Thanks!
> > +{
> > + return test_bit(NAPI_STATE_SCHED, &n->state);
> > +}
> > +
> > bool napi_schedule_prep(struct napi_struct *n);
> >
> > /**
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index cc03a5758d2d..32ba8002f65a 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -6523,7 +6523,7 @@ static int __napi_poll(struct napi_struct *n, bool *repoll)
> > * accidentally calling ->poll() when NAPI is not scheduled.
> > */
> > work = 0;
> > - if (test_bit(NAPI_STATE_SCHED, &n->state)) {
> > + if (napi_is_scheduled(n)) {
> > work = n->poll(n, weight);
> > trace_napi_poll(n, work, weight);
> > }
> > --
> > 2.40.1
> >
--
Ansuel
