Date: Sat, 23 Sep 2000 16:37:51 -0700 (PDT) From: John Baldwin <jhb@FreeBSD.ORG> To: Chuck Paterson <cp@bsdi.com> Cc: freebsd-arch@FreeBSD.ORG, freebsd-net@FreeBSD.ORG, Bosko Milekic <bmilekic@technokratis.com> Subject: Re: mbuf system and SMPng Message-ID: <XFMail.000923163751.jhb@FreeBSD.org> In-Reply-To: <200009232243.QAA19490@berserker.bsdi.com>
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On 23-Sep-00 Chuck Paterson wrote: > > Date: Sat, 23 Sep 2000 14:46:44 -0400 > From: Bosko Milekic <bmilekic@technokratis.com> > To: Chuck Paterson <cp@bsdi.com> > Subject: Re: mbuf system and SMPng > cc: freebsd-net@FreeBSD.ORG, freebsd-arch@FreeBSD.ORG > > Bosko Milekic wrote on: Sat, 23 Sep 2000 14:46:44 EDT > > } Indeed, the lock being released before the asleep() being called in > } m_mballoc_wait() is somewhat of a race. I was planning to get rid of the > } asleep/await combo anyway (noted in my journal). In fact, MGET() can be > } called even with the mutex held, it will just result in recursive > } grabbing of the mutex, but it's better to just re-arrange the macro with > } a lower-level one, as you say (I noticed BSD/OS does something like > } this). > } > > One thing to remember about the recursive stuff is that > passing a recursively held mutex to msleep() will not get the > mutex released, it will only release it one time. This means > that you likely won't be able to get a wakeup. This could > be changed, but ->>in general<<- something has gone very wrong > if the mutex passed in to msleep() is recursively held. There > is likely a layer of code that is expecting that its data is protected, > and is not expecting some other process to be able to get at it. Hmm, do we want to add a KASSERT() to msleep() then to verify that the mutex isn't recursed when we release it? > Chuck -- John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/ PGP Key: http://www.cslab.vt.edu/~jobaldwi/pgpkey.asc "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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