Date: Sun, 4 Jul 2004 01:34:38 -0400 From: Brian Fundakowski Feldman <green@FreeBSD.org> To: Bosko Milekic <bmilekic@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/vm uma_core.c Message-ID: <20040704053438.GB964@green.homeunix.org> In-Reply-To: <20040704042027.GA94373@freefall.freebsd.org> References: <20040704042027.GA94373@freefall.freebsd.org>
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On Sun, Jul 04, 2004 at 04:20:27AM +0000, Bosko Milekic wrote: > > This change is bogus. It checks uz_name against "Mbuf" but mbuma also > defines a "Packet" zone. > > Even if that were fixed, I would personally prefer a backout. The > original intent of this [temporary] piece of code is to help detect > potential deadlocks and make sure that they don't happen, as they are > generally tougher to debug than traps on NULL pointer dereferences. > The fact that without WITNESS M_WAITOK is actually overriden by > M_NOWAIT behavior, although conservative, ensures that deadlock due > to, say, locks being held while sleeping. > > The need for the temporary code is still significant because we still > have code paths that could potentially lead to deadlock here. I'd > rather proactively, albeit conservatively, avoid that deadlock, knowing > that the situation where even M_NOWAIT will return NULL should not > occur unless I have heavy/unexpected load anyway. > > With that said, I would agree to you adding a way to have badness on > 0 by default, possibly by making it a debug boot-time tunable, or > better, rw-sysctl. Backing this out is inappropriate -- malloc(WAITOK) may never fail. Please further correct behavior for mbufs, but don't break malloc/zalloc for everyone as it was when EVER returning NULL for WAITOK. -- Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\ <> green@FreeBSD.org \ The Power to Serve! \ Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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