From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: [PATCH] [FOR 4.2] tmem: add matching unlock for an about-to-be-destroyed object Date: Fri, 31 Aug 2012 21:08:58 +0100 Message-ID: References: <76edd759-ceca-4fb5-b411-1e598137afd8@default> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <76edd759-ceca-4fb5-b411-1e598137afd8@default> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Dan Magenheimer , xen-devel@lists.xen.org Cc: Zhenzhong Duan , Konrad Rzeszutek Wilk List-Id: xen-devel@lists.xenproject.org On 31/08/2012 20:58, "Dan Magenheimer" wrote: > (Guidance appreciated if the Xen patch submittal process > has changed and I need to do more than send this email.) This is fine, thanks! -- Keir > A 4.2 changeset forces a preempt_disable/enable with > every lock/unlock. > > Tmem has dynamically allocated "objects" that contain a > lock. The lock is held when the object is destroyed. > No reason to unlock something that's about to be destroyed! > But with the preempt_enable/disable in the generic locking code, > and the fact that do_softirq ASSERTs that preempt_count > must be zero, a crash occurs soon after any object is > destroyed. > > So force lock to be released before destroying objects. > > Signed-off-by: Dan Magenheimer > > diff -r 1967c7c290eb xen/common/tmem.c > --- a/xen/common/tmem.c Wed Feb 09 12:03:09 2011 +0000 > +++ b/xen/common/tmem.c Fri Aug 31 13:49:51 2012 -0600 > @@ -957,6 +957,7 @@ > /* use no_rebalance only if all objects are being destroyed anyway */ > if ( !no_rebalance ) > rb_erase(&obj->rb_tree_node,&pool->obj_rb_root[oid_hash(&old_oid)]); > + tmem_spin_unlock(&obj->obj_spinlock); > tmem_free(obj,sizeof(obj_t),pool); > } >