Date: Wed, 03 Nov 2010 15:01:16 -0700 From: Julian Elischer <julian@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: mdf@freebsd.org, freebsd-current@freebsd.org, Andriy Gapon <avg@icyb.net.ua> Subject: Re: MTX_DEF versus MTX_SPIN Message-ID: <4CD1DBAC.6050004@freebsd.org> In-Reply-To: <4CD1A14E.8060508@freebsd.org> References: <AANLkTi=12-dSAZ21DbZgw36YbRGiUq4KZbyCx3SjucPG@mail.gmail.com> <4CD190EF.5080600@icyb.net.ua> <AANLkTimmiQ9VH=cr%2BPJ4Hz=h1Oua%2Bouj7CAv8L__JeNn@mail.gmail.com> <201011031317.36332.jhb@freebsd.org> <4CD1A14E.8060508@freebsd.org>
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On 11/3/10 10:52 AM, Julian Elischer wrote: > On 11/3/10 10:17 AM, John Baldwin wrote: >> On Wednesday, November 03, 2010 1:04:13 pm mdf@freebsd.org wrote: >>> >>> So a MTX_DEF is okay in that environment? >> Yes. In fact, the reason to have threads for interrupt handlers is >> to allow >> interrupt handlers to use non-spin locks that block when the lock >> is held. >> >> MTX_SPIN locks are generally not needed in device drivers. The >> only reason a >> driver would use one is if it used a filter handler which does not >> run in a >> threaded context. > oops a line got deleted I think.. > It should be noted that in the case where you really just want to > spin a few > instructions because some other thread is accessing a structure you > want, ... then the BTX_DEF code will spin for a short while before ... > descheduling you. so you don't always incur the scheduling overhead. > > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to > "freebsd-current-unsubscribe@freebsd.org" >
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