On Fri, Oct 6, 2023 at 8:49 PM Christian Marangi <[email protected]> wrote:
>
> On Thu, Oct 05, 2023 at 06:16:26PM +0200, Eric Dumazet wrote:
> > On Tue, Oct 3, 2023 at 8:36 PM Christian Marangi <[email protected]> wrote:
> > >
> > > Replace if condition of napi_schedule_prep/__napi_schedule and use bool
> > > from napi_schedule directly where possible.
> > >
> > > Signed-off-by: Christian Marangi <[email protected]>
> > > ---
> > > drivers/net/ethernet/atheros/atlx/atl1.c | 4 +---
> > > drivers/net/ethernet/toshiba/tc35815.c | 4 +---
> > > drivers/net/wireless/intel/iwlwifi/pcie/rx.c | 4 +---
> > > 3 files changed, 3 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/atheros/atlx/atl1.c b/drivers/net/ethernet/atheros/atlx/atl1.c
> > > index 02aa6fd8ebc2..a9014d7932db 100644
> > > --- a/drivers/net/ethernet/atheros/atlx/atl1.c
> > > +++ b/drivers/net/ethernet/atheros/atlx/atl1.c
> > > @@ -2446,7 +2446,7 @@ static int atl1_rings_clean(struct napi_struct *napi, int budget)
> > >
> > > static inline int atl1_sched_rings_clean(struct atl1_adapter* adapter)
> > > {
> > > - if (!napi_schedule_prep(&adapter->napi))
> > > + if (!napi_schedule(&adapter->napi))
> > > /* It is possible in case even the RX/TX ints are disabled via IMR
> > > * register the ISR bits are set anyway (but do not produce IRQ).
> > > * To handle such situation the napi functions used to check is
> > > @@ -2454,8 +2454,6 @@ static inline int atl1_sched_rings_clean(struct atl1_adapter* adapter)
> > > */
> > > return 0;
> > >
> > > - __napi_schedule(&adapter->napi);
> > > -
> > > /*
> > > * Disable RX/TX ints via IMR register if it is
> > > * allowed. NAPI handler must reenable them in same
> > > diff --git a/drivers/net/ethernet/toshiba/tc35815.c b/drivers/net/ethernet/toshiba/tc35815.c
> > > index 14cf6ecf6d0d..a8b8a0e13f9a 100644
> > > --- a/drivers/net/ethernet/toshiba/tc35815.c
> > > +++ b/drivers/net/ethernet/toshiba/tc35815.c
> > > @@ -1436,9 +1436,7 @@ static irqreturn_t tc35815_interrupt(int irq, void *dev_id)
> > > if (!(dmactl & DMA_IntMask)) {
> > > /* disable interrupts */
> > > tc_writel(dmactl | DMA_IntMask, &tr->DMA_Ctl);
> > > - if (napi_schedule_prep(&lp->napi))
> > > - __napi_schedule(&lp->napi);
> > > - else {
> > > + if (!napi_schedule(&lp->napi)) {
> > > printk(KERN_ERR "%s: interrupt taken in poll\n",
> > > dev->name);
> > > BUG();
> >
> > Hmmm... could you also remove this BUG() ? I think this code path can be taken
> > if some applications are using busy polling.
> >
> > Or simply rewrite this with the traditional
> >
> > if (napi_schedule_prep(&lp->napi)) {
> > /* disable interrupts */
> > tc_writel(dmactl | DMA_IntMask, &tr->DMA_Ctl);
> > __napi_schedule(&lp->napi);
> > }
> >
> >
>
> Mhhh is it safe to do so? I mean it seems very wrong to print a warning
> and BUG() instead of disabling the interrupt only if napi can be
> scheduled... Maybe is very old code? The more I see this the more I see
> problem... (randomly disabling the interrupt and then make the kernel
> die)
I am pretty sure this BUG() can be hit these days with busy polling or
setting gro_flush_timeout.
I wish we could remove these bugs before someone copy-paste them.
Again, this is orthogonal, I might simply stop doing reviews if this
is not useful.