Date: Thu, 1 Dec 2016 18:20:55 -0500 From: David Windsor <dwindsor@...il.com> To: Peter Zijlstra <peterz@...radead.org> Cc: "Reshetova, Elena" <elena.reshetova@...el.com>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Greg KH <gregkh@...uxfoundation.org>, Kees Cook <keescook@...omium.org>, "will.deacon@....com" <will.deacon@....com>, Boqun Feng <boqun.feng@...il.com>, Hans Liljestrand <ishkamiel@...il.com>, "aik@...abs.ru" <aik@...abs.ru>, "david@...son.dropbear.id.au" <david@...son.dropbear.id.au> Subject: Re: Conversion from atomic_t to refcount_t: summary of issues On Thu, Dec 1, 2016 at 6:03 PM, Peter Zijlstra <peterz@...radead.org> wrote: > > On Thu, Dec 01, 2016 at 04:31:16PM -0500, David Windsor wrote: > > Also, I'd like to point out that while identifying stats_t instances, I > > have found a similar distribution of non-standard functions (as agreed upon > > for the stats_t API). > > > First, usage of atomic_long_wrap_t (there currently isn't a stats_long_t > > planned for implementation): > > There isn't even a stats_t planned. I'm still very much not convinced > stats_t is needed or even makes sense. > > It wouldn't have any different semantics from atomic_t, and the only > argument Kees made was that reduced atomic_t usage would make it easier > to spot refcounts, but you're already building tools to find those. > Then are we decided that overflow protection is going to be opt-in? If atomic_t isn't protected by default (opt-in case), then yes, new users will have no need to use a type other than atomic_t for their shared statistical counters. > Once the tools work, who cares. > > > Next, API calls outside of the proposed stats_t API: > > > > kernel/auditsc.c:2029: > > if (uid_valid(loginuid)) > > sessionid = (unsigned int)atomic_inc_return_wrap(&session_id); > > This is _NOT_ a statistic counter and should not be stats_t > > > kernel/padata.c:58: > > seq_nr = atomic_inc_return_wrap(&pd->seq_nr); > > Idem > > > kernel/rcu/tree_trace.c:192: > > s0 += atomic_long_read_wrap(&rdp->exp_workdone0); > > Don't get the point, this one is actually trivial. > > > kernel/trace/trace_mmiotrace.c:123 > > atomic_xchg_wrap(&dropped_count, 0); > > > > ... and several others. Note, these are only from stats_t conversions in > > the kernel/ directory. > > And while that thing counts, its not actually a statistics thing.
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.