On Fri, Dec 09, 2016 at 02:12:00PM +0900, Byungchul Park wrote: > add_chain_cache() should be used in the context where the hlock is > owned since it might be racy in another context. However crossrelease > feature needs to build a chain between two locks regardless of context. > So introduce a new function making it possible. > > Signed-off-by: Byungchul Park <[email protected]> > --- > kernel/locking/lockdep.c | 56 > ++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 56 insertions(+) > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index 5df56aa..111839f 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -2105,6 +2105,62 @@ static int check_no_collision(struct task_struct *curr, > return 1; > } > > +/* > + * This is for building a chain between just two different classes, > + * instead of adding a new hlock upon current, which is done by > + * add_chain_cache(). > + * > + * This can be called in any context with two classes, while > + * add_chain_cache() must be done within the lock owener's context > + * since it uses hlock which might be racy in another context. > + */ > +static inline int add_chain_cache_classes(unsigned int prev, > + unsigned int next, > + unsigned int irq_context, > + u64 chain_key) > +{ > + struct hlist_head *hash_head = chainhashentry(chain_key); > + struct lock_chain *chain; > + > + /* > + * Allocate a new chain entry from the static array, and add > + * it to the hash: > + */ > + > + /* > + * We might need to take the graph lock, ensure we've got IRQs > + * disabled to make this an IRQ-safe lock.. for recursion reasons > + * lockdep won't complain about its own locking errors. > + */ > + if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) > + return 0; > + > + if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) { > + if (!debug_locks_off_graph_unlock()) > + return 0; > + > + print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!"); > + dump_stack(); > + return 0; > + } > + > + chain = lock_chains + nr_lock_chains++; > + chain->chain_key = chain_key; > + chain->irq_context = irq_context; > + chain->depth = 2; > + if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) > { > + chain->base = nr_chain_hlocks; > + nr_chain_hlocks += chain->depth; > + chain_hlocks[chain->base] = prev - 1; > + chain_hlocks[chain->base + 1] = next -1; > + }
You didn't copy this part right. There is no error when > MAX_LOCKDEP_CHAIN_HLOCKS. > + hlist_add_head_rcu(&chain->entry, hash_head); > + debug_atomic_inc(chain_lookup_misses); > + inc_chains(); > + > + return 1; > +} > + > static inline int add_chain_cache(struct task_struct *curr, > struct held_lock *hlock, > u64 chain_key) > -- > 1.9.1 >
