Date: Thu, 21 May 2009 09:42:34 -0400 From: John Baldwin <jhb@freebsd.org> To: Attilio Rao <attilio@freebsd.org> Cc: Kostik Belousov <kostikbel@gmail.com>, svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r192535 - head/sys/kern Message-ID: <200905210942.35555.jhb@freebsd.org> In-Reply-To: <3bbf2fe10905210629p46c7a204v6863aaba77354462@mail.gmail.com> References: <200905211322.n4LDM73t067924@svn.freebsd.org> <20090521132641.GJ1927@deviant.kiev.zoral.com.ua> <3bbf2fe10905210629p46c7a204v6863aaba77354462@mail.gmail.com>
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On Thursday 21 May 2009 9:29:57 am Attilio Rao wrote: > 2009/5/21 Kostik Belousov <kostikbel@gmail.com>: > > On Thu, May 21, 2009 at 01:22:07PM +0000, Attilio Rao wrote: > >> Author: attilio > >> Date: Thu May 21 13:22:07 2009 > >> New Revision: 192535 > >> URL: http://svn.freebsd.org/changeset/base/192535 > >> > >> Log: > >> Move the M_WAITOK flag in notify() into an M_NOWAIT one in order to match > >> the behaviour alredy present with the further malloc() call in > >> devctl_notify(). > >> This fixes a bug in the CAM layer where the camisr handler finished to > >> call camperiphfree() (and subsequently destroy_dev() resulting in a new > >> dev notify) while the xpt lock is held. > > This is wrong. You cannot call destroy_dev() while holding any mutex. > > Taking this into account, it makes no sense to use M_NOWAIT in notify(). > > As long as devctl_notify() also calls M_NOWAIT and if not available > skips "silently" it just does the same thing, I think this approach is > more consistent. > > It remains, though, the fact to fix CAM when calling destroy_dev(). > Maybe we should add a witness_warn() there? I agree with kib, this should be reverted and CAM fixed instead. I also agree that M_NOWAIT use should be limited where possible. -- John Baldwin
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