Date: Wed, 5 Mar 2014 15:29:55 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Gleb Smirnoff <glebius@freebsd.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org> Subject: Re: svn commit: r262806 - head/sys/net Message-ID: <CAJ-Vmomz1ikt9=2pDFsnR0uu2HhJ%2BUj%2BrcW7O-fxve_qT05Umw@mail.gmail.com> In-Reply-To: <201403052116.s25LGkEq007924@svn.freebsd.org> References: <201403052116.s25LGkEq007924@svn.freebsd.org>
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... why's the code returning locked mutexes to UMA? Why not fix the places that are doing this and doing a lock assertion in the destructor? What's this buy us? I'm very wary of design patterns like this that do conditional unlocking in free/destructor routines; it allows for the caller to not necessarily get all the lock/unlock stuff to line up in the main code and it can make debugging more of a pain. Thanks, -a On 5 March 2014 13:16, Gleb Smirnoff <glebius@freebsd.org> wrote: > Author: glebius > Date: Wed Mar 5 21:16:46 2014 > New Revision: 262806 > URL: http://svnweb.freebsd.org/changeset/base/262806 > > Log: > The route code used to mtx_destroy() a locked mutex before rtentry free. Now, > after r262763 it started to return locked mutexes to UMA. To fix that, > conditionally unlock the mutex in the destructor. > > Tested by: "Sergey V. Dyatko" <sergey.dyatko@gmail.com> > > Modified: > head/sys/net/route.c > head/sys/net/route.h > > Modified: head/sys/net/route.c > ============================================================================== > --- head/sys/net/route.c Wed Mar 5 20:01:04 2014 (r262805) > +++ head/sys/net/route.c Wed Mar 5 21:16:46 2014 (r262806) > @@ -237,6 +237,14 @@ rtentry_ctor(void *mem, int size, void * > } > > static void > +rtentry_dtor(void *mem, int size, void *arg) > +{ > + struct rtentry *rt = mem; > + > + RT_UNLOCK_COND(rt); > +} > + > +static void > vnet_route_init(const void *unused __unused) > { > struct domain *dom; > @@ -248,7 +256,7 @@ vnet_route_init(const void *unused __unu > sizeof(struct radix_node_head *), M_RTABLE, M_WAITOK|M_ZERO); > > V_rtzone = uma_zcreate("rtentry", sizeof(struct rtentry), > - rtentry_ctor, NULL, > + rtentry_ctor, rtentry_dtor, > rtentry_zinit, rtentry_zfini, UMA_ALIGN_PTR, 0); > for (dom = domains; dom; dom = dom->dom_next) { > if (dom->dom_rtattach == NULL) > > Modified: head/sys/net/route.h > ============================================================================== > --- head/sys/net/route.h Wed Mar 5 20:01:04 2014 (r262805) > +++ head/sys/net/route.h Wed Mar 5 21:16:46 2014 (r262806) > @@ -309,6 +309,10 @@ struct rt_addrinfo { > #define RT_UNLOCK(_rt) mtx_unlock(&(_rt)->rt_mtx) > #define RT_LOCK_DESTROY(_rt) mtx_destroy(&(_rt)->rt_mtx) > #define RT_LOCK_ASSERT(_rt) mtx_assert(&(_rt)->rt_mtx, MA_OWNED) > +#define RT_UNLOCK_COND(_rt) do { \ > + if (mtx_owned(&(_rt)->rt_mtx)) \ > + mtx_unlock(&(_rt)->rt_mtx); \ > +} while (0) > > #define RT_ADDREF(_rt) do { \ > RT_LOCK_ASSERT(_rt); \ >
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