From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH] lockdep: annotate rcu_read_{,un}lock() Date: Thu, 16 Aug 2007 09:01:45 -0700 Message-ID: <20070816160145.GA16957@linux.vnet.ibm.com> References: <20070815.144628.104052147.davem@davemloft.net> <1187274307.6114.92.camel@twins> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ingo Molnar , herbert@gondor.apana.org.au, 123.oleg@gmail.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, David Miller , Daniel Walker , josht@linux.vnet.ibm.com To: Peter Zijlstra Return-path: Received: from e5.ny.us.ibm.com ([32.97.182.145]:33944 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765588AbXHPQBt (ORCPT ); Thu, 16 Aug 2007 12:01:49 -0400 Content-Disposition: inline In-Reply-To: <1187274307.6114.92.camel@twins> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, Aug 16, 2007 at 04:25:07PM +0200, Peter Zijlstra wrote: > > There seem to be some unbalanced rcu_read_{,un}lock() issues of late, > how about doing something like this: This will break when rcu_read_lock() and rcu_read_unlock() are invoked from NMI/SMI handlers -- the raw_local_irq_save() in lock_acquire() will not mask NMIs or SMIs. One approach would be to check for being in an NMI/SMI handler, and to avoid calling lock_acquire() and lock_release() in those cases. Another approach would be to use sparse, which has checks for rcu_read_lock()/rcu_read_unlock() nesting. Thanx, Paul > Signed-off-by: Peter Zijlstra > --- > include/linux/lockdep.h | 7 +++++++ > include/linux/rcupdate.h | 12 ++++++++++++ > kernel/rcupdate.c | 8 ++++++++ > 3 files changed, 27 insertions(+) > > Index: linux-2.6/include/linux/lockdep.h > =================================================================== > --- linux-2.6.orig/include/linux/lockdep.h > +++ linux-2.6/include/linux/lockdep.h > @@ -252,6 +252,13 @@ extern void lockdep_init_map(struct lock > struct lock_class_key *key, int subclass); > > /* > + * To initialize a lockdep_map statically use this macro. > + * Note that _name must not be NULL. > + */ > +#define STATIC_LOCKDEP_MAP_INIT(_name, _key) \ > + { .name = (_name), .key = (void *)(_key), } > + > +/* > * Reinitialize a lock key - for cases where there is special locking or > * special initialization of locks so that the validator gets the scope > * of dependencies wrong: they are either too broad (they need a class-split) > Index: linux-2.6/include/linux/rcupdate.h > =================================================================== > --- linux-2.6.orig/include/linux/rcupdate.h > +++ linux-2.6/include/linux/rcupdate.h > @@ -41,6 +41,7 @@ > #include > #include > #include > +#include > > /** > * struct rcu_head - callback structure for use with RCU > @@ -133,6 +134,15 @@ static inline void rcu_bh_qsctr_inc(int > extern int rcu_pending(int cpu); > extern int rcu_needs_cpu(int cpu); > > +#ifdef CONFIG_DEBUG_LOCK_ALLOC > +extern struct lockdep_map rcu_lock_map; > +# define rcu_read_acquire() lock_acquire(&rcu_lock_map, 0, 0, 2, 1, _THIS_IP_) > +# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) > +#else > +# define rcu_read_acquire() do { } while (0) > +# define rcu_read_release() do { } while (0) > +#endif > + > /** > * rcu_read_lock - mark the beginning of an RCU read-side critical section. > * > @@ -166,6 +176,7 @@ extern int rcu_needs_cpu(int cpu); > do { \ > preempt_disable(); \ > __acquire(RCU); \ > + rcu_read_acquire(); \ > } while(0) > > /** > @@ -175,6 +186,7 @@ extern int rcu_needs_cpu(int cpu); > */ > #define rcu_read_unlock() \ > do { \ > + rcu_read_release(); \ > __release(RCU); \ > preempt_enable(); \ > } while(0) > Index: linux-2.6/kernel/rcupdate.c > =================================================================== > --- linux-2.6.orig/kernel/rcupdate.c > +++ linux-2.6/kernel/rcupdate.c > @@ -49,6 +49,14 @@ > #include > #include > > +#ifdef CONFIG_DEBUG_LOCK_ALLOC > +static struct lock_class_key rcu_lock_key; > +struct lockdep_map rcu_lock_map = > + STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); > + > +EXPORT_SYMBOL_GPL(rcu_lock_map); > +#endif > + > /* Definition for rcupdate control block. */ > static struct rcu_ctrlblk rcu_ctrlblk = { > .cur = -300, > > > - > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html