Date: Fri, 2 Dec 2016 00:03:28 +0100 From: Peter Zijlstra <peterz@...radead.org> To: David Windsor <dwindsor@...il.com> 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 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. 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.
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