Messages in this thread | | | Date | Mon, 25 Sep 2017 08:44:04 -0700 | From | Tejun Heo <> | Subject | Re: [PATCH] percpu: make this_cpu_generic_read() atomic w.r.t. interrupts |
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Hello,
On Mon, Sep 25, 2017 at 04:33:02PM +0100, Mark Rutland wrote: > Unfortunately, the generic this_cpu_read(), which is intended to be > irq-safe, is not: > > #define this_cpu_generic_read(pcp) \ > ({ \ > typeof(pcp) __ret; \ > preempt_disable_notrace(); \ > __ret = raw_cpu_generic_read(pcp); \ > preempt_enable_notrace(); \ > __ret; \ > })
I see. Yeah, that looks like the bug there.
> I guess it'd be preferable to manipulate that in-place. > > > Adding READ_ONCE() doesn't generically guarantee that the reads won't > > be split - e.g. there are arch which simply can't load a 64bit value > > with a single instruction. > > In which case, it really sounds like this_cpu_generic_read() needs to > disable interrupts too...
Can you please spin up a patch for this?
Thanks.
-- tejun
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