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Groups > linux.kernel > #1227711
| From | Will Deacon <will.deacon@arm.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] kernel: fix data race in put_pid |
| Date | 2015-09-18 11:30 +0200 |
| Message-ID | <qa09t-6UG-29@gated-at.bofh.it> (permalink) |
| References | (3 earlier) <q9LtN-2jP-29@gated-at.bofh.it> <q9LDs-2vw-17@gated-at.bofh.it> <q9LWN-38s-1@gated-at.bofh.it> <q9ZGr-67w-31@gated-at.bofh.it> <q9ZQ7-6yg-41@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Fri, Sep 18, 2015 at 10:06:46AM +0100, Dmitry Vyukov wrote:
> On Fri, Sep 18, 2015 at 10:51 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > As an alternative patch, could we not do:
> >
> > void put_pid(struct pid *pid)
> > {
> > struct pid_namespace *ns;
> >
> > if (!pid)
> > return;
> >
> > ns = pid->numbers[pid->level].ns;
> > if ((atomic_read(&pid->count) == 1) ||
> > atomic_dec_and_test(&pid->count)) {
> >
> > + smp_read_barrier_depends(); /* ctrl-dep */
> >
> > kmem_cache_free(ns->pid_cachep, pid);
> > put_pid_ns(ns);
> > }
> > }
> >
> > That would upgrade the atomic_read() path to a full READ_ONCE_CTRL(),
> > and thereby avoid any of the kmem_cache_free() stores from leaking out.
> > And its free, except on Alpha. Whereas the atomic_read_acquire() will
> > generate a full memory barrier on whole bunch of archs.
>
>
> What you propose makes sense.
>
> +Will, Paul
>
> Can we have something along the lines of:
>
> #define atomic_read_ctrl(v) READ_ONCE_CTRL(&(v)->counter)
Funnily enough, I had this exact same discussion off-list yesterday
afternoon, since I wrote some code relying on a ctrl dependency from
an atomic_read to an atomic_xchg_relaxed.
So I guess I'm for the addition, but at the same time, could we make
atomic_read and atomic_set generic too?
Will
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[PATCH] kernel: fix data race in put_pid Dmitry Vyukov <dvyukov@google.com> - 2015-09-17 15:30 +0200
Re: [PATCH] kernel: fix data race in put_pid Oleg Nesterov <oleg@redhat.com> - 2015-09-17 18:20 +0200
Re: [PATCH] kernel: fix data race in put_pid Dmitry Vyukov <dvyukov@google.com> - 2015-09-17 18:50 +0200
Re: [PATCH] kernel: fix data race in put_pid Oleg Nesterov <oleg@redhat.com> - 2015-09-17 19:50 +0200
Re: [PATCH] kernel: fix data race in put_pid Dmitry Vyukov <dvyukov@google.com> - 2015-09-17 20:00 +0200
Re: [PATCH] kernel: fix data race in put_pid Dmitry Vyukov <dvyukov@google.com> - 2015-09-17 20:10 +0200
Re: [PATCH] kernel: fix data race in put_pid Oleg Nesterov <oleg@redhat.com> - 2015-09-17 20:20 +0200
Re: [PATCH] kernel: fix data race in put_pid Dmitry Vyukov <dvyukov@google.com> - 2015-09-17 20:40 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 11:00 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 11:10 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 11:40 +0200
Re: [PATCH] kernel: fix data race in put_pid James Hogan <james.hogan@imgtec.com> - 2015-09-18 14:40 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 14:50 +0200
Re: [PATCH] kernel: fix data race in put_pid "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-09-18 18:40 +0200
Re: [PATCH] kernel: fix data race in put_pid Dmitry Vyukov <dvyukov@google.com> - 2015-09-18 11:10 +0200
Re: [PATCH] kernel: fix data race in put_pid Will Deacon <will.deacon@arm.com> - 2015-09-18 11:30 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 11:40 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 13:30 +0200
Re: [PATCH] kernel: fix data race in put_pid Will Deacon <will.deacon@arm.com> - 2015-09-18 13:40 +0200
Re: [PATCH] kernel: fix data race in put_pid Dmitry Vyukov <dvyukov@google.com> - 2015-09-18 14:00 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 14:10 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 14:30 +0200
Re: [PATCH] kernel: fix data race in put_pid Will Deacon <will.deacon@arm.com> - 2015-09-18 14:50 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 15:20 +0200
Re: [PATCH] kernel: fix data race in put_pid Oleg Nesterov <oleg@redhat.com> - 2015-09-18 15:50 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 16:00 +0200
Re: [PATCH] kernel: fix data race in put_pid Dmitry Vyukov <dvyukov@google.com> - 2015-09-18 16:00 +0200
Re: [PATCH] kernel: fix data race in put_pid Oleg Nesterov <oleg@redhat.com> - 2015-09-18 16:50 +0200
Re: [PATCH] kernel: fix data race in put_pid Dmitry Vyukov <dvyukov@google.com> - 2015-09-22 10:40 +0200
Re: [PATCH] kernel: fix data race in put_pid Eric Dumazet <eric.dumazet@gmail.com> - 2015-09-18 18:20 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 18:30 +0200
Re: [PATCH] kernel: fix data race in put_pid "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-09-18 18:00 +0200
Re: [PATCH] kernel: fix data race in put_pid Oleg Nesterov <oleg@redhat.com> - 2015-09-18 15:40 +0200
Re: [PATCH] kernel: fix data race in put_pid Oleg Nesterov <oleg@redhat.com> - 2015-09-18 15:40 +0200
Re: [PATCH] kernel: fix data race in put_pid Peter Zijlstra <peterz@infradead.org> - 2015-09-18 16:00 +0200
Re: [PATCH] kernel: fix data race in put_pid Oleg Nesterov <oleg@redhat.com> - 2015-09-18 17:10 +0200
Re: [PATCH] kernel: fix data race in put_pid Oleg Nesterov <oleg@redhat.com> - 2015-09-18 17:40 +0200
Re: [PATCH] kernel: fix data race in put_pid "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-09-18 18:30 +0200
Re: [PATCH] kernel: fix data race in put_pid "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-09-17 20:00 +0200
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