lockdep: add lock_class information to lock_chain and output it

This patch records array of lock_class into lock_chain, and export
lock_chain information via /proc/lockdep_chains.

It is based on x86/master branch of git-x86 tree, and has been tested
on x86_64 platform.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 132 insertions, 3 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 81a4e4a3f087..a796f1f38ac5 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -1458,7 +1458,14 @@ out_bug:
 }
 
 unsigned long nr_lock_chains;
-static struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
+struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
+atomic_t nr_chain_hlocks;
+static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
+
+struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
+{
+        return lock_classes + chain_hlocks[chain->base + i];
+}
 
 /*
  * Look up a dependency chain. If the key is not present yet then
@@ -1466,10 +1473,15 @@ static struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
  * validated. If the key is already hashed, return 0.
  * (On return with 1 graph_lock is held.)
  */
-static inline int lookup_chain_cache(u64 chain_key, struct lock_class *class)
+static inline int lookup_chain_cache(struct task_struct *curr,
+                                     struct held_lock *hlock,
+                                     u64 chain_key)
 {
+        struct lock_class *class = hlock->class;
         struct list_head *hash_head = chainhashentry(chain_key);
         struct lock_chain *chain;
+        struct held_lock *hlock_curr, *hlock_next;
+        int i, j, n;
 
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return 0;
@@ -1517,6 +1529,26 @@ cache_hit:
         }
         chain = lock_chains + nr_lock_chains++;
         chain->chain_key = chain_key;
+        chain->irq_context = hlock->irq_context;
+        /* Find the first held_lock of current chain */
+        hlock_next = hlock;
+        for (i = curr->lockdep_depth - 1; i >= 0; i--) {
+                hlock_curr = curr->held_locks + i;
+                if (hlock_curr->irq_context != hlock_next->irq_context)
+                        break;
+                hlock_next = hlock;
+        }
+        i++;
+        chain->depth = curr->lockdep_depth + 1 - i;
+        n = atomic_add_return(chain->depth, &nr_chain_hlocks);
+        if (unlikely(n < MAX_LOCKDEP_CHAIN_HLOCKS)) {
+                chain->base = n - chain->depth;
+                for (j = 0; j < chain->depth - 1; j++, i++) {
+                        int lock_id = curr->held_locks[i].class - lock_classes;
+                        chain_hlocks[chain->base + j] = lock_id;
+                }
+                chain_hlocks[chain->base + j] = class - lock_classes;
+        }
         list_add_tail_rcu(&chain->entry, hash_head);
         debug_atomic_inc(&chain_lookup_misses);
         inc_chains();
@@ -1538,7 +1570,7 @@ static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
          * graph_lock for us)
          */
         if (!hlock->trylock && (hlock->check == 2) &&
-                        lookup_chain_cache(chain_key, hlock->class)) {
+            lookup_chain_cache(curr, hlock, chain_key)) {
                 /*
                  * Check whether last held lock:
                  *
diff --git a/kernel/lockdep_internals.h b/kernel/lockdep_internals.h
index 8ce09bc4613d..db09b176dd34 100644
--- a/kernel/lockdep_internals.h
+++ b/kernel/lockdep_internals.h
@@ -23,6 +23,8 @@
 #define MAX_LOCKDEP_CHAINS_BITS 14
 #define MAX_LOCKDEP_CHAINS      (1UL << MAX_LOCKDEP_CHAINS_BITS)
 
+#define MAX_LOCKDEP_CHAIN_HLOCKS (MAX_LOCKDEP_CHAINS*5)
+
 /*
  * Stack-trace: tightly packed array of stack backtrace
  * addresses. Protected by the hash_lock.
@@ -30,15 +32,19 @@
 #define MAX_STACK_TRACE_ENTRIES 262144UL
 
 extern struct list_head all_lock_classes;
+extern struct lock_chain lock_chains[];
 
 extern void
 get_usage_chars(struct lock_class *class, char *c1, char *c2, char *c3, char *c4);
 
 extern const char * __get_key_name(struct lockdep_subclass_key *key, char *str);
 
+struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i);
+
 extern unsigned long nr_lock_classes;
 extern unsigned long nr_list_entries;
 extern unsigned long nr_lock_chains;
+extern atomic_t nr_chain_hlocks;
 extern unsigned long nr_stack_trace_entries;
 
 extern unsigned int nr_hardirq_chains;
diff --git a/kernel/lockdep_proc.c b/kernel/lockdep_proc.c
index 688c5f1940bd..14d052c8a835 100644
--- a/kernel/lockdep_proc.c
+++ b/kernel/lockdep_proc.c
@@ -178,6 +178,93 @@ static const struct file_operations proc_lockdep_operations = {
         .release        = seq_release,
 };
 
+static void *lc_next(struct seq_file *m, void *v, loff_t *pos)
+{
+        struct lock_chain *chain;
+
+        (*pos)++;
+
+        if (v == SEQ_START_TOKEN)
+                chain = m->private;
+        else {
+                chain = v;
+
+                if (*pos < nr_lock_chains)
+                        chain = lock_chains + *pos;
+                else
+                        chain = NULL;
+        }
+
+        return chain;
+}
+
+static void *lc_start(struct seq_file *m, loff_t *pos)
+{
+        if (*pos == 0)
+                return SEQ_START_TOKEN;
+
+        if (*pos < nr_lock_chains)
+                return lock_chains + *pos;
+
+        return NULL;
+}
+
+static void lc_stop(struct seq_file *m, void *v)
+{
+}
+
+static int lc_show(struct seq_file *m, void *v)
+{
+        struct lock_chain *chain = v;
+        struct lock_class *class;
+        int i;
+
+        if (v == SEQ_START_TOKEN) {
+                seq_printf(m, "all lock chains:\n");
+                return 0;
+        }
+
+        seq_printf(m, "irq_context: %d\n", chain->irq_context);
+
+        for (i = 0; i < chain->depth; i++) {
+                class = lock_chain_get_class(chain, i);
+                seq_printf(m, "[%p] ", class->key);
+                print_name(m, class);
+                seq_puts(m, "\n");
+        }
+        seq_puts(m, "\n");
+
+        return 0;
+}
+
+static const struct seq_operations lockdep_chains_ops = {
+        .start  = lc_start,
+        .next   = lc_next,
+        .stop   = lc_stop,
+        .show   = lc_show,
+};
+
+static int lockdep_chains_open(struct inode *inode, struct file *file)
+{
+        int res = seq_open(file, &lockdep_chains_ops);
+        if (!res) {
+                struct seq_file *m = file->private_data;
+
+                if (nr_lock_chains)
+                        m->private = lock_chains;
+                else
+                        m->private = NULL;
+        }
+        return res;
+}
+
+static const struct file_operations proc_lockdep_chains_operations = {
+        .open           = lockdep_chains_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = seq_release,
+};
+
 static void lockdep_stats_debug_show(struct seq_file *m)
 {
 #ifdef CONFIG_DEBUG_LOCKDEP
@@ -294,6 +381,8 @@ static int lockdep_stats_show(struct seq_file *m, void *v)
 #ifdef CONFIG_PROVE_LOCKING
         seq_printf(m, " dependency chains:             %11lu [max: %lu]\n",
                         nr_lock_chains, MAX_LOCKDEP_CHAINS);
+        seq_printf(m, " dependency chain hlocks:       %11d [max: %lu]\n",
+                        atomic_read(&nr_chain_hlocks), MAX_LOCKDEP_CHAIN_HLOCKS);
 #endif
 
 #ifdef CONFIG_TRACE_IRQFLAGS
@@ -661,6 +750,8 @@ static const struct file_operations proc_lock_stat_operations = {
 static int __init lockdep_proc_init(void)
 {
         proc_create("lockdep", S_IRUSR, NULL, &proc_lockdep_operations);
+        proc_create("lockdep_chains", S_IRUSR, NULL,
+                    &proc_lockdep_chains_operations);
         proc_create("lockdep_stats", S_IRUSR, NULL,
                     &proc_lockdep_stats_operations);