On Wed, Feb 19, 2020 at 01:56:02PM +0100, Jan Beulich wrote:
> On 13.02.2020 12:32, Roger Pau Monne wrote:
> > void __init register_cpu_notifier(struct notifier_block *nb)
> > {
> > - if ( !spin_trylock(&cpu_add_remove_lock) )
> > + if ( !write_trylock(&cpu_add_remove_lock) )
> > BUG(); /* Should never fail as we are called only during boot. */
> > notifier_chain_register(&cpu_chain, nb);
> > - spin_unlock(&cpu_add_remove_lock);
> > + write_unlock(&cpu_add_remove_lock);
> > }
>
> So why a write lock here?
notifier_chain_register calls cannot be made in parallel, as they
modify the underlying notifier list without taking any additional
locks.
Thanks, Roger.
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