Date: Mon, 19 May 2008 09:15:00 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-drivers@freebsd.org Cc: n4ti1us <gaspar_i@yahoo.com> Subject: Re: Spin locks and software IRQs. Message-ID: <200805190915.00902.jhb@freebsd.org> In-Reply-To: <17277776.post@talk.nabble.com> References: <17277776.post@talk.nabble.com>
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On Friday 16 May 2008 11:37:46 am n4ti1us wrote: > Hi All, > > I was looking at the linux kernel, and in the implementation of spinlocks, > one can use different functions. One of them is spin_lock_bh(). What it > does is it creates a spin lock and disables the software irqs. > > In FreeBSD on the other hand, the implementation of spinlocks is done by > mtx_lock_spin (which is actually a macro that calls mtx_lock_spin_flags()) > but the problem is that is disables all the irq vector (at the bottom of > the stack it executes an "cli"). Is there any way one can implement > spinlocks that only disable the bottom half (sof irq)? > > Alternatively, what would be the best way to manualy disable the soft irqs? > > And all this makes me think... Why has nobody implemented a "_bh" version > so far? Is this an architectural decision, or is it just me being blind? Generally one should use a regular mutex to protect data. Spin locks in FreeBSD are only used by scheduler internals or for a driver that has to interact with an INTR_FAST handler (or filter in 7.x+). -- John Baldwin
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