Re: [PATCH for-4.10] common/spinlock: Improve the output from check_lock() if it trips

[Julien Grall <julien.grall@linaro.org>]

Hi Andrew,

On 31/10/17 10:49, Andrew Cooper wrote:
> If check_lock() triggers, a crash will occur.  Instead of simply identifying
> "the irq context was different", indicate the expected and current irq
> context.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Release-acked-by: Julien Grall <julien.grall@linaro.org>

Cheers,

> ---
> CC: George Dunlap <George.Dunlap@eu.citrix.com>
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> CC: Stefano Stabellini <sstabellini@kernel.org>
> CC: Tim Deegan <tim@xen.org>
> CC: Wei Liu <wei.liu2@citrix.com>
> CC: Julien Grall <julien.grall@arm.com>
> 
> check_lock() only exists in debug builds, which makes this a low risk change
> for 4.10.
> ---
>   xen/common/spinlock.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/common/spinlock.c b/xen/common/spinlock.c
> index 44b07b7..8f2ba08 100644
> --- a/xen/common/spinlock.c
> +++ b/xen/common/spinlock.c
> @@ -44,7 +44,13 @@ static void check_lock(struct lock_debug *debug)
>       if ( unlikely(debug->irq_safe != irq_safe) )
>       {
>           int seen = cmpxchg(&debug->irq_safe, -1, irq_safe);
> -        BUG_ON(seen == !irq_safe);
> +
> +        if ( seen == !irq_safe )
> +        {
> +            printk("CHECKLOCK FAILURE: prev irqsafe: %d, curr irqsafe %d\n",
> +                   seen, irq_safe);
> +            BUG();
> +        }
>       }
>   }
>   
> 

-- 
Julien Grall

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