Re: [Xen-devel] [PATCH 2/2] xen/mce: fix static variable 'severity_cpu'

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

On 04/06/17 02:06 -0600, Jan Beulich wrote:
> >>> On 06.04.17 at 06:55, <haozhong.zhang@xxxxxxxxx> wrote:
> > 1. Distinguish 'severity_cpu' used in mcheck_cmn_handler() and
> >    mce_softirq(), which should be different variables. Otherwise, they
> >    may interfere with each other if MC# comes during mce_softirq().
> > 2. Always (re-)initialize 'severity_cpu' to clear historical information.
> 
> I agree with this for the mcheck_cmn_handler() case, but ...
> 
> > @@ -1704,11 +1703,16 @@ static int mce_delayed_action(mctelem_cookie_t mctc)
> >  /* Softirq Handler for this MCE# processing */
> >  static void mce_softirq(void)
> >  {
> > +    static atomic_t severity_cpu;
> >      int cpu = smp_processor_id();
> >      unsigned int workcpu;
> >  
> >      mce_printk(MCE_VERBOSE, "CPU%d enter softirq\n", cpu);
> >  
> > +    mce_barrier_enter(&mce_softirq_init_bar);
> > +    atomic_set(&severity_cpu, -1);
> > +    mce_barrier_exit(&mce_softirq_init_bar);
> 
> ... I don't think this is needed, as right after the following comment
> it'll be set unconditionally.
>
> > @@ -1774,6 +1778,7 @@ void mce_handler_init(void)
> >      mce_barrier_init(&mce_severity_bar);
> >      mce_barrier_init(&mce_trap_bar);
> >      mce_barrier_init(&mce_handler_init_bar);
> > +    mce_barrier_init(&mce_softirq_init_bar);
> 
> Just like the variables you move, all these mce_*_bar ones are
> really private to their respective functions. I've taken a not to
> put together a patch to move the pre-existing ones, but please
> don't introduce any new ones with file scope.
>

How is about introducing a static initializer for mce barrier so that
I can initialize static ones at their declaration? Or is the static
initializer completely not needed because all fields of mce barrier
are currently initialized to 0?

Thanks,
Haozhong

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