From: Eric Dumazet <eric.duma...@gmail.com> Date: Wed, 01 May 2013 08:24:03 -0700
> [PATCH v2] af_unix: fix a fatal race with bit fields > > Using bit fields is dangerous on ppc64/sparc64, as the compiler [1] > 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. > > A safer way would be to use a long to store flags. > This way we are sure compiler/arch wont do bad things. > > As we own unix_gc_lock spinlock when clearing or setting bits, > we can use the non atomic __set_bit()/__clear_bit(). > > recursion_level can share the same 64bit location with the spinlock, > as it is set only with this spinlock held. > > [1] bug fixed in gcc-4.8.0 : > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52080 > > Reported-by: Ambrose Feinstein <ambr...@google.com> > Signed-off-by: Eric Dumazet <eduma...@google.com> Applied and queued up for -stable, thanks Eric. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
