On Thu, Oct 11, 2018 at 8:50 AM Peter Zijlstra wrote:
> Right; it goes back a long long way... is:
>
> 7c3576d261ce ("[PATCH] i386: Convert PDA into the percpu section")
>
> early enough? That introduces percpu_from_op(), but arguably the
> pda_from_op() it replaces was buggy already.
Yeah I
On Thu, Oct 11, 2018 at 8:50 AM Peter Zijlstra wrote:
> Right; it goes back a long long way... is:
>
> 7c3576d261ce ("[PATCH] i386: Convert PDA into the percpu section")
>
> early enough? That introduces percpu_from_op(), but arguably the
> pda_from_op() it replaces was buggy already.
Yeah I
On Thu, Oct 11, 2018 at 08:24:49AM -0700, Eric Dumazet wrote:
> On Thu, Oct 11, 2018 at 8:02 AM Eric Dumazet wrote:
> >
> > On Thu, Oct 11, 2018 at 3:45 AM Peter Zijlstra wrote:
> > >
> > > Eric reported that a sequence count loop using this_cpu_read() got
> > > optimized out. This is wrong,
On Thu, Oct 11, 2018 at 08:24:49AM -0700, Eric Dumazet wrote:
> On Thu, Oct 11, 2018 at 8:02 AM Eric Dumazet wrote:
> >
> > On Thu, Oct 11, 2018 at 3:45 AM Peter Zijlstra wrote:
> > >
> > > Eric reported that a sequence count loop using this_cpu_read() got
> > > optimized out. This is wrong,
On Thu, Oct 11, 2018 at 8:02 AM Eric Dumazet wrote:
>
> On Thu, Oct 11, 2018 at 3:45 AM Peter Zijlstra wrote:
> >
> > Eric reported that a sequence count loop using this_cpu_read() got
> > optimized out. This is wrong, this_cpu_read() must imply READ_ONCE()
> > because the interface is IRQ-safe,
On Thu, Oct 11, 2018 at 8:02 AM Eric Dumazet wrote:
>
> On Thu, Oct 11, 2018 at 3:45 AM Peter Zijlstra wrote:
> >
> > Eric reported that a sequence count loop using this_cpu_read() got
> > optimized out. This is wrong, this_cpu_read() must imply READ_ONCE()
> > because the interface is IRQ-safe,
On Thu, Oct 11, 2018 at 3:45 AM Peter Zijlstra wrote:
>
> Eric reported that a sequence count loop using this_cpu_read() got
> optimized out. This is wrong, this_cpu_read() must imply READ_ONCE()
> because the interface is IRQ-safe, therefore an interrupt can have
> changed the per-cpu value.
>
>
On Thu, Oct 11, 2018 at 3:45 AM Peter Zijlstra wrote:
>
> Eric reported that a sequence count loop using this_cpu_read() got
> optimized out. This is wrong, this_cpu_read() must imply READ_ONCE()
> because the interface is IRQ-safe, therefore an interrupt can have
> changed the per-cpu value.
>
>
Eric reported that a sequence count loop using this_cpu_read() got
optimized out. This is wrong, this_cpu_read() must imply READ_ONCE()
because the interface is IRQ-safe, therefore an interrupt can have
changed the per-cpu value.
Fixes: 59eaef78bfea ("x86/tsc: Remodel cyc2ns to use
Eric reported that a sequence count loop using this_cpu_read() got
optimized out. This is wrong, this_cpu_read() must imply READ_ONCE()
because the interface is IRQ-safe, therefore an interrupt can have
changed the per-cpu value.
Fixes: 59eaef78bfea ("x86/tsc: Remodel cyc2ns to use
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