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 <[EMAIL PROTECTED]> > --- > 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 <linux/percpu.h> > #include <linux/cpumask.h> > #include <linux/seqlock.h> > +#include <linux/lockdep.h> > > /** > * 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 <linux/cpu.h> > #include <linux/mutex.h> > > +#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 [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html