Date: Mon, 11 Feb 2002 19:06:44 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: John Baldwin <jhb@FreeBSD.org> Cc: Alfred Perlstein <bright@mu.org>, current@freebsd.org, bde@freebsd.org, Julian Elischer <julian@elischer.org> Subject: Re: ucred holding patch, BDE version Message-ID: <3C6886C4.B2B08C5B@mindspring.com> References: <XFMail.020211203102.jhb@FreeBSD.org>
next in thread | previous in thread | raw e-mail | index | archive | help
John Baldwin wrote: > Yes, calling free() without Giant is about as good as calling fdrop() without > Giant Alfred. :) Alfred would be right, for per processor memory pools. 8-). > >> And on the way into the system it does: > >> lock process > >> crhold() (which includes mutex ops) > >> unlock process > > > > This isn't needed, at least afaik. > > Not strictly for the comparison as Julian and Terry pointed out since the race > can occur anyway (i.e., you don't need the lock to see if p_ucred changed), > however, if you are actually doing a crhold(), you want to make sure p_ucred > isn't stale, so you need the proc lock. No. If you _depend_ on the frequency of change being low, you can do this with only atomic reference counts. See the pseudo code in my other posting, in direct response to you. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3C6886C4.B2B08C5B>