Date: Fri, 27 Sep 2002 17:20:27 -0400 (EDT) From: John Baldwin <jhb@FreeBSD.org> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: current@freebsd.org Subject: RE: Freedom from Giant for (most^H^H^H^Hsome) driver writers! Message-ID: <XFMail.20020927172027.jhb@FreeBSD.org> In-Reply-To: <18849.1033156603@critter.freebsd.dk>
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On 27-Sep-2002 Poul-Henning Kamp wrote: > 4. It may not even work at all in the first place. We havn't done > the VFS locking yet, so dropping giant in specfs may open a pathway > to the dungeon-dimensions (this is a bad thing). I actually implemented this very early on during SMPng (a flag in the cdevsw) but we ended up not committing it for this reason. You can only do this if you assume the calling code doesn't make any assumptions about interrupts being blocked. IOW, in 4.x terms, if cdevsw routines are always called at spl0 then this is safe. If they aren't, then, well, this isn't safe yet. :) -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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