On Mon, 6 Jul 2020 13:23:11 +0200 Halil Pasic <pa...@linux.ibm.com> wrote:
> On Fri, 3 Jul 2020 12:06:49 +0200 > Cornelia Huck <coh...@redhat.com> wrote: > > > From: Halil Pasic <pa...@linux.ibm.com> > > > > The atomic_cmpxchg() loop is broken because we occasionally end up with > > old and _old having different values (a legit compiler can generate code > > that accessed *ind_addr again to pick up a value for _old instead of > > using the value of old that was already fetched according to the > > rules of the abstract machine). This means the underlying CS instruction > > may use a different old (_old) than the one we intended to use if > > atomic_cmpxchg() performed the xchg part. > > > > Let us use volatile to force the rules of the abstract machine for > > accesses to *ind_addr. Let us also rewrite the loop so, we that the > > Michael T. Has pointed out that this sentence is ungrammatical. > > s/we// would IMHO solve the problem. Can we fix this before it gets > merged? Unfortunately, it's already too late :( > > > new old is used to compute the new desired value if the xchg part > > is not performed.
