tech-kern: Re: SMP re-entrancy in kernel drivers/"bottom half?"

Subject: Re: SMP re-entrancy in kernel drivers/"bottom half?"
To: None <jonathan@DSG.Stanford.EDU>
From: YAMAMOTO Takashi <yamt@mwd.biglobe.ne.jp>
List: tech-kern
Date: 12/18/2003 07:50:38

hi,

>     * acquire a spinlock when raising IPL to IPL_NET or above
>       (one per hardware IPL). Raising IPl requires acquiring all spinlocks
>       between current IPL and target, in order to prevent deadlocks.
>       release  all the spinlocks in reverse order at the corresponding splx().

why need to acquire all spinlocks between them?
i can't imagine how it deadlocks.

YAMAMOTO Takashi