Re: [PATCH] Revert "seqlock: lockdep assert non-preemptibility on seqcount_t write"

Greg KH
2020-08-10T10:04:53Z

On Mon, Aug 10, 2020 at 11:54:28AM +0200, Ahmed S. Darwish wrote:
> This reverts commit 859247d39fb008ea812e8f0c398a58a20c12899e.
>
> Current implementation of lockdep_assert_preemption_disabled() uses
> per-CPU variables, which was done to untangle the existing
> seqlock.h<=>sched.h 'current->' task_struct circular dependency.
>
> Using per-CPU variables did not fully untangle the dependency for
> various non-x86 architectures though, resulting in multiple broken
> builds. For the affected architectures, raw_smp_processor_id() led
> back to 'current->', thus having the original seqlock.h<=>sched.h
> dependency in full-effect.
>
> For now, revert adding lockdep_assert_preemption_disabled() to
> seqlock.h.
>
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Link: https://lkml.kernel.org/r/20200808232122.GA176509@roeck-us.net
> Link: https://lkml.kernel.org/r/20200810085954.GA1591892@kroah.com
> References: Commit a21ee6055c30 ("lockdep: Change hardirq{s_enabled,_context} to per-cpu variables")
> Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Even after this, there are still some build errors on arm32, but I don't
think they are due to this change:

ERROR: modpost: "__aeabi_uldivmod" [drivers/net/ethernet/sfc/sfc.ko] undefined!
ERROR: modpost: "__bad_udelay" [drivers/net/ethernet/aquantia/atlantic/atlantic.ko] undefined!

thanks,

greg k-h