=EF=BB=BFThis patch is not intended to be merged. Just hope it is useful fo=
r
somebody want to investigate kernel locking behavior. The simple
scripts attached with the mail can be used to draw class chain graph
via graphviz.
Best Regards,
Huang Ying
------------------------------------------------------------->
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>
---
include/linux/lockdep.h | 3 +
kernel/lockdep.c | 38 +++++++++++++++++-
kernel/lockdep_internals.h | 6 ++
kernel/lockdep_proc.c | 91 ++++++++++++++++++++++++++++++++++++++++=
+++++
4 files changed, 135 insertions(+), 3 deletions(-)
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -1463,7 +1463,14 @@ out_bug:
}
=20
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];
+}
=20
/*
* Look up a dependency chain. If the key is not present yet then
@@ -1471,10 +1478,15 @@ static struct lock_chain lock_chains[MAX
* 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 *cla=
ss)
+static inline int lookup_chain_cache(struct task_struct *curr,
+ struct held_lock *hlock,
+ u64 chain_key)
{
+ struct lock_class *class =3D hlock->class;
struct list_head *hash_head =3D chainhashentry(chain_key);
struct lock_chain *chain;
+ struct held_lock *hlock_curr, *hlock_next;
+ int i, j, n;
=20
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return 0;
@@ -1522,6 +1534,26 @@ cache_hit:
}
chain =3D lock_chains + nr_lock_chains++;
chain->chain_key =3D chain_key;
+ chain->irq_context =3D hlock->irq_context;
+ /* Find the first held_lock of current chain */
+ hlock_next =3D hlock;
+ for (i =3D curr->lockdep_depth - 1; i >=3D 0; i--) {
+ hlock_curr =3D curr->held_locks + i;
+ if (hlock_curr->irq_context !=3D hlock_next->irq_context)
+ break;
+ hlock_next =3D hlock;
+ }
+ i++;
+ chain->depth =3D curr->lockdep_depth + 1 - i;
+ n =3D atomic_add_return(chain->depth, &nr_chain_hlocks);
+ if (unlikely(n < MAX_LOCKDEP_CHAIN_HLOCKS)) {
+ chain->base =3D n - chain->depth;
+ for (j =3D 0; j < chain->depth - 1; j++, i++) {
+ int lock_id =3D curr->held_locks[i].class - lock_classes;
+ chain_hlocks[chain->base + j] =3D lock_id;
+ }
+ chain_hlocks[chain->base + j] =3D class - lock_classes;
+ }
list_add_tail_rcu(&chain->entry, hash_head);
debug_atomic_inc(&chain_lookup_misses);
inc_chains();
@@ -1543,7 +1575,7 @@ static int validate_chain(struct task_st
* graph_lock for us)
*/
if (!hlock->trylock && (hlock->check =3D=3D 2) &&
- lookup_chain_cache(chain_key, hlock->class)) {
+ lookup_chain_cache(curr, hlock, chain_key)) {
/*
* Check whether last held lock:
*
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -182,6 +182,9 @@ struct lock_list {
* We record lock dependency chains, so that we can cache them:
*/
struct lock_chain {
+ u8 irq_context;
+ u8 depth;
+ u16 base;
struct list_head entry;
u64 chain_key;
};
--- a/kernel/lockdep_proc.c
+++ b/kernel/lockdep_proc.c
@@ -178,6 +178,93 @@ static const struct file_operations proc
.release =3D seq_release,
};
=20
+static void *lc_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ struct lock_chain *chain;
+
+ (*pos)++;
+
+ if (v =3D=3D SEQ_START_TOKEN)
+ chain =3D m->private;
+ else {
+ chain =3D v;
+
+ if (*pos < nr_lock_chains)
+ chain =3D lock_chains + *pos;
+ else
+ chain =3D NULL;
+ }
+
+ return chain;
+}
+
+static void *lc_start(struct seq_file *m, loff_t *pos)
+{
+ if (*pos =3D=3D 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 =3D v;
+ struct lock_class *class;
+ int i;
+
+ if (v =3D=3D SEQ_START_TOKEN) {
+ seq_printf(m, "all lock chains:\n");
+ return 0;
+ }
+
+ seq_printf(m, "irq_context: %d\n", chain->irq_context);
+
+ for (i =3D 0; i < chain->depth; i++) {
+ class =3D 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 =3D {
+ .start =3D lc_start,
+ .next =3D lc_next,
+ .stop =3D lc_stop,
+ .show =3D lc_show,
+};
+
+static int lockdep_chains_open(struct inode *inode, struct file *file)
+{
+ int res =3D seq_open(file, &lockdep_chains_ops);
+ if (!res) {
+ struct seq_file *m =3D file->private_data;
+
+ if (nr_lock_chains)
+ m->private =3D lock_chains;
+ else
+ m->private =3D NULL;
+ }
+ return res;
+}
+
+static const struct file_operations proc_lockdep_chains_operations =3D {
+ .open =3D lockdep_chains_open,
+ .read =3D seq_read,
+ .llseek =3D seq_lseek,
+ .release =3D 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
#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
=20
#ifdef CONFIG_TRACE_IRQFLAGS
@@ -661,6 +750,8 @@ static const struct file_operations proc
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);
=20
--- 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)
=20
+#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
=20
extern struct list_head all_lock_classes;
+extern struct lock_chain lock_chains[];
=20
extern void
get_usage_chars(struct lock_class *class, char *c1, char *c2, char *c3, ch=
ar *c4);
=20
extern const char * __get_key_name(struct lockdep_subclass_key *key, char =
*str);
=20
+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;
=20
extern unsigned int nr_hardirq_chains;
