On Fri, 2013-05-03 at 11:01 +0930, Alan Modra wrote: > On Tue, Apr 30, 2013 at 10:04:32PM -0700, Eric Dumazet wrote: > > These kind of errors are pretty hard to find, its a pity to spend time > > on them. > > Well, yes. From the first comment in gcc PR52080. "For the following > testcase we generate a 8 byte RMW cycle on IA64 which causes locking > problems in the linux kernel btrfs filesystem." > > Did someone fix btrfs, but not check other kernel locks? Having now > hit the same problem again, have you checked that other kernel locks > don't have adjacent bit fields in the same 64-bit word? And comment > the struct to ensure someone doesn't optimize those unsigned chars > back to bit fields.
Not only spinlock, but atomic_t followed by bit fields. BTW, if a spinlock is followed by bit fields, but bit fields only changed when this spinlock is held, there is no problem, unless spinlock is a ticket spinlock. In af_unix, bug happens because the bit fields were changed without spinlock being held (another global spinlock is used instead) (ppc64 doesnt use ticket spinlocks yet) _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
