Re: [PATCH] ARM: keystone: add a work around to handle asynchronous external abort

[Murali Karicheri]

On 08/14/2015 05:56 PM, Russell King - ARM Linux wrote:
> On Fri, Aug 14, 2015 at 05:55:09PM -0400, Murali Karicheri wrote:
> > On 08/14/2015 10:20 AM, Lucas Stach wrote:
> > > Hi Russell,
> > >
> > > Am Freitag, den 14.08.2015, 15:09 +0100 schrieb Russell King - ARM
> > > Linux:
> > >
> > > [...]
> > >
> > > > What causes the abort?  We shouldn't be adding hacks like this to the
> > > > kernel without having the full picture...
> > >
> > > some of the issues with tracking down such imprecise external aborts are
> > > due to the fact that we only enable the signaling of those aborts on
> > > entering the user-space. So the first schedule() crashes on the previous
> > > dangling abort.
> > >
> > > I'm carrying this patch locally to enable imprecise aborts much earlier
> > > in the boot process. I think it has already been on the list some times,
> > > but apparently it has fallen through the cracks. If you agree that this
> > > is the right thing to do I can do a proper repost.
> > Lucas,
> >
> > Would you mind sharing the code? Does that help in root causing where it
> > actually happens? I have spend considerable time debugging this, but so far
> > not successful.
>
> If you look below, Lucas provided the patch.
Oops! Thanks

Murali

> > Murali
> > > Regards,
> > > Lucas
> > >
> > > ---------------------->8---------------------------------------------
> > > >From bb9117d94cc2f1061dc364f42c446ccd9191e869 Mon Sep 17 00:00:00 2001
> > > From: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> > > Date: Thu, 19 Feb 2015 18:12:50 +0100
> > > Subject: [PATCH] ARM: Add imprecise abort enable/disable macro
> > >
> > > This patch adds imprecise abort enable/disable macros.
> > > It also enables imprecise aborts when starting kernel.
> > >
> > > Changes in v2:
> > > Only ARMv6 and later have CPSR.A bit. On earlier CPUs,
> > > and ARMv7M this should be a no-op.
> > >
> > > Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
> > > Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> > > ---
> > > lst: rebased on v3.19
> > > ---
> > >   arch/arm/include/asm/irqflags.h | 10 ++++++++++
> > >   arch/arm/kernel/smp.c           |  1 +
> > >   arch/arm/kernel/traps.c         |  4 ++++
> > >   3 files changed, 15 insertions(+)
> > >
> > > diff --git a/arch/arm/include/asm/irqflags.h
> > > b/arch/arm/include/asm/irqflags.h
> > > index 3b763d6652a0..8301f875564e 100644
> > > --- a/arch/arm/include/asm/irqflags.h
> > > +++ b/arch/arm/include/asm/irqflags.h
> > > @@ -51,6 +51,14 @@ static inline void arch_local_irq_disable(void)
> > >
> > >   #define local_fiq_enable()  __asm__("cpsie f   @ __stf" : : : "memory",
> > > "cc")
> > >   #define local_fiq_disable() __asm__("cpsid f   @ __clf" : : : "memory",
> > > "cc")
> > > +
> > > +#ifndef CONFIG_CPU_V7M
> > > +#define local_abt_enable()  __asm__("cpsie a   @ __sta" : : : "memory",
> > > "cc")
> > > +#define local_abt_disable() __asm__("cpsid a   @ __cla" : : : "memory",
> > > "cc")
> > > +#else
> > > +#define local_abt_enable()     do { } while (0)
> > > +#define local_abt_disable()    do { } while (0)
> > > +#endif
> > >   #else
> > >
> > >   /*
> > > @@ -130,6 +138,8 @@ static inline void arch_local_irq_disable(void)
> > >          : "memory", "cc");                                      \
> > >          })
> > >
> > > +#define local_abt_enable()     do { } while (0)
> > > +#define local_abt_disable()    do { } while (0)
> > >   #endif
> > >
> > >   /*
> > > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> > > index 86ef244c5a24..7b6b93cabef4 100644
> > > --- a/arch/arm/kernel/smp.c
> > > +++ b/arch/arm/kernel/smp.c
> > > @@ -378,6 +378,7 @@ asmlinkage void secondary_start_kernel(void)
> > >
> > >          local_irq_enable();
> > >          local_fiq_enable();
> > > +       local_abt_enable();
> > >
> > >          /*
> > >           * OK, it's off to the idle thread for us
> > > diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
> > > index 788e23fe64d8..466726ba9bdb 100644
> > > --- a/arch/arm/kernel/traps.c
> > > +++ b/arch/arm/kernel/traps.c
> > > @@ -881,6 +881,10 @@ void __init early_trap_init(void *vectors_base)
> > >
> > >          flush_icache_range(vectors, vectors + PAGE_SIZE * 2);
> > >          modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
> > > +
> > > +       /* Enable imprecise aborts */
> > > +       local_abt_enable();
> > > +
> > >   #else /* ifndef CONFIG_CPU_V7M */
> > >          /*
> > >           * on V7-M there is no need to copy the vector table to a
> > > dedicated
> >
> >
> > --
> > Murali Karicheri
> > Linux Kernel, Keystone


--
Murali Karicheri
Linux Kernel, Keystone
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/