Hi Eric, > From: Eric Dumazet <eduma...@google.com> > > Using bit fields is dangerous on ppc64, as the compiler uses 64bit > instructions to manipulate them. If the 64bit word includes any > atomic_t or spinlock_t, we can lose critical concurrent changes. > > This is happening in af_unix, where unix_sk(sk)->gc_candidate/ > gc_maybe_cycle/lock share the same 64bit word. > > This leads to fatal deadlock, as one/several cpus spin forever > on a spinlock that will never be available again.
I just spoke to Alan Modra and he suspects this is a compiler bug. Can you give us your compiler version info? Anton > Reported-by: Ambrose Feinstein <ambr...@google.com> > Signed-off-by: Eric Dumazet <eduma...@google.com> > Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org> > Cc: Paul Mackerras <pau...@samba.org> > --- > > Could ppc64 experts confirm using byte is safe, or should we really > add a 32bit hole after the spinlock ? If so, I wonder how many other > places need a change... > > include/net/af_unix.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/net/af_unix.h b/include/net/af_unix.h > index a8836e8..4520a23f 100644 > --- a/include/net/af_unix.h > +++ b/include/net/af_unix.h > @@ -57,8 +57,8 @@ struct unix_sock { > struct list_head link; > atomic_long_t inflight; > spinlock_t lock; > - unsigned int gc_candidate : 1; > - unsigned int gc_maybe_cycle : 1; > + unsigned char gc_candidate; > + unsigned char gc_maybe_cycle; > unsigned char recursion_level; > struct socket_wq peer_wq; > }; > > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev