Re: [Xen-devel] [PATCH v5 1/5] xen/spinlocks: in debug builds store cpu holding the lock

[Jan Beulich <jbeulich@xxxxxxxx>]

On 12.09.2019 15:28, Juergen Gross wrote:
> @@ -267,6 +288,7 @@ int _spin_trylock_recursive(spinlock_t *lock)
>  
>      /* Don't allow overflow of recurse_cpu field. */
>      BUILD_BUG_ON(NR_CPUS > SPINLOCK_NO_CPU);
> +    BUILD_BUG_ON(SPINLOCK_RECURSE_BITS <= 0);

This is too weak: While I don't think we strictly need 15 levels of
recursion, I also don't think we'll get away with just 1. I think
this minimally needs to be "<= 1", perhaps better "<= 2". Other
thoughts (also by others) on the precise value to use here
appreciated. With this suitably taken care of (which can happen
while committing, but must not be forgotten)
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan

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