RE: [PATCH] soc: fsl: dpio: protect smp_processor_id when get processor id

["Li, Meng" <Meng.Li@windriver.com>]

> -----Original Message-----
> From: Robin Murphy <robin.murphy@arm.com>
> Sent: Friday, October 15, 2021 9:40 PM
> To: Li, Meng <Meng.Li@windriver.com>; Roy.Pledge@nxp.com;
> leoyang.li@nxp.com; ruxandra.radulescu@nxp.com; horia.geanta@nxp.com
> Cc: linux-kernel@vger.kernel.org; linuxppc-dev@lists.ozlabs.org; linux-arm-
> kernel@lists.infradead.org
> Subject: Re: [PATCH] soc: fsl: dpio: protect smp_processor_id when get
> processor id
> 
> [Please note: This e-mail is from an EXTERNAL e-mail address]
> 
> On 2021-10-15 07:36, Meng.Li@windriver.com wrote:
> > From: Meng Li <meng.li@windriver.com>
> >
> > When enable debug kernel configs,there will be calltrace as below:
> >
> > BUG: using smp_processor_id() in preemptible [00000000] code:
> > swapper/0/1 caller is debug_smp_processor_id+0x20/0x30
> > CPU: 6 PID: 1 Comm: swapper/0 Not tainted 5.10.63-yocto-standard #1
> > Hardware name: NXP Layerscape LX2160ARDB (DT) Call trace:
> >   dump_backtrace+0x0/0x1a0
> >   show_stack+0x24/0x30
> >   dump_stack+0xf0/0x13c
> >   check_preemption_disabled+0x100/0x110
> >   debug_smp_processor_id+0x20/0x30
> >   dpaa2_io_query_fq_count+0xdc/0x154
> >   dpaa2_eth_stop+0x144/0x314
> >   __dev_close_many+0xdc/0x160
> >   __dev_change_flags+0xe8/0x220
> >   dev_change_flags+0x30/0x70
> >   ic_close_devs+0x50/0x78
> >   ip_auto_config+0xed0/0xf10
> >   do_one_initcall+0xac/0x460
> >   kernel_init_freeable+0x30c/0x378
> >   kernel_init+0x20/0x128
> >   ret_from_fork+0x10/0x38
> >
> > Because smp_processor_id() should be invoked in preempt disable status.
> > So, add preempt_disable/enable() to protect smp_processor_id().
> 
> If preemption doesn't matter anyway, as the comment in the context implies,
> then it probably makes more sense just to use
> raw_smp_processor_id() instead.
> 

Thanks for your professional suggest, I will raw_smp_processor_id() and test.
If works fine, I will send v2 patch.

Thanks,
Limeng

> Robin.
> 
> > Fixes: c89105c9b390 ("staging: fsl-mc: Move DPIO from staging to
> > drivers/soc/fsl")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Meng Li <Meng.Li@windriver.com>
> > ---
> >   drivers/soc/fsl/dpio/dpio-service.c | 7 +++++--
> >   1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/soc/fsl/dpio/dpio-service.c
> > b/drivers/soc/fsl/dpio/dpio-service.c
> > index 19f47ea9dab0..afc3b89b0fc5 100644
> > --- a/drivers/soc/fsl/dpio/dpio-service.c
> > +++ b/drivers/soc/fsl/dpio/dpio-service.c
> > @@ -58,8 +58,11 @@ static inline struct dpaa2_io
> *service_select_by_cpu(struct dpaa2_io *d,
> >        * If cpu == -1, choose the current cpu, with no guarantees about
> >        * potentially being migrated away.
> >        */
> > -     if (cpu < 0)
> > -             cpu = smp_processor_id();
> > +        if (cpu < 0) {
> > +                preempt_disable();
> > +                cpu = smp_processor_id();
> > +                preempt_enable();
> > +        }
> >
> >       /* If a specific cpu was requested, pick it up immediately */
> >       return dpio_by_cpu[cpu];
> >