Michael Ellerman <[email protected]> writes: > In commit 407821a we assigned a poison value to the paca->data_offset. > > Unfortunately with CONFIG_LOCK_STAT=y lockdep will read & write to percpu > data very early in boot, prior to us initialising the percpu areas, > leading to a crash. > > We have been getting away with this because the data_offset was previously > set to zero. This causes lockdep to read & write to the initial copy of > the percpu variables, which are discarded later in boot. > > Although that is "fishy", it does work, and for lock statistics it is no > big deal to discard the counts from early boot. > > So set the paca->data_offset = 0 for the boot cpu paca only. > > Reported-by: Aneesh Kumar K.V <[email protected]> > Signed-off-by: Michael Ellerman <[email protected]>
Tested-by: Aneesh Kumar K.V <[email protected]> > --- > arch/powerpc/kernel/setup_64.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c > index 389bd4f..efb6a41 100644 > --- a/arch/powerpc/kernel/setup_64.c > +++ b/arch/powerpc/kernel/setup_64.c > @@ -208,6 +208,8 @@ void __init early_setup(unsigned long dt_ptr) > > /* Fix up paca fields required for the boot cpu */ > get_paca()->cpu_start = 1; > + /* Allow percpu accesses to "work" until we setup percpu data */ > + get_paca()->data_offset = 0; > > /* Probe the machine type */ > probe_machine(); > -- > 1.7.9.5 _______________________________________________ Linuxppc-dev mailing list [email protected] https://lists.ozlabs.org/listinfo/linuxppc-dev
