Re: [PATCH] rhashtable: Fix potential deadlock by moving schedule_work outside lock

[Herbert Xu]

On Thu, Nov 28, 2024 at 04:16:25AM -0800, Breno Leitao wrote:
> Move the hash table growth check and work scheduling outside the
> rht lock to prevent a possible circular locking dependency.
> 
> The original implementation could trigger a lockdep warning due to
> a potential deadlock scenario involving nested locks between
> rhashtable bucket, rq lock, and dsq lock. By relocating the
> growth check and work scheduling after releasing the rth lock, we break
> this potential deadlock chain.
> 
> This change expands the flexibility of rhashtable by removing
> restrictive locking that previously limited its use in scheduler
> and workqueue contexts.

Could you please explain the deadlock? Is the workqueue system actually
using rhashtable?

Thanks,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
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