[PATCH 03/19] lockdep: improve scenario messages for RECLAIM_FS errors.

NeilBrown
2014-04-16T04:18:13Z

lockdep can check for locking problems involving reclaim using
the same infrastructure as used for interrupts.

However a number of the messages still refer to interrupts even
if it was actually a reclaim-related problem.

So determine where the problem was caused by reclaim or irq and adjust
messages accordingly.

Signed-off-by: NeilBrown <neilb@suse.de>
---
kernel/locking/lockdep.c | 43 ++++++++++++++++++++++++++++++++-----------
1 file changed, 32 insertions(+), 11 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index e05b82e92373..33d2ac7519dc 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1423,7 +1423,8 @@ static void
print_irq_lock_scenario(struct lock_list *safe_entry,
struct lock_list *unsafe_entry,
struct lock_class *prev_class,
- struct lock_class *next_class)
+ struct lock_class *next_class,
+ int reclaim)
{
struct lock_class *safe_class = safe_entry->class;
struct lock_class *unsafe_class = unsafe_entry->class;
@@ -1455,20 +1456,27 @@ print_irq_lock_scenario(struct lock_list *safe_entry,
printk("\n\n");
}

- printk(" Possible interrupt unsafe locking scenario:\n\n");
+ if (reclaim)
+ printk(" Possible reclaim unsafe locking scenario:\n\n");
+ else
+ printk(" Possible interrupt unsafe locking scenario:\n\n");
printk(" CPU0 CPU1\n");
printk(" ---- ----\n");
printk(" lock(");
__print_lock_name(unsafe_class);
printk(");\n");
- printk(" local_irq_disable();\n");
+ if (!reclaim)
+ printk(" local_irq_disable();\n");
printk(" lock(");
__print_lock_name(safe_class);
printk(");\n");
printk(" lock(");
__print_lock_name(middle_class);
printk(");\n");
- printk(" <Interrupt>\n");
+ if (reclaim)
+ printk(" <Memory allocation/reclaim>\n");
+ else
+ printk(" <Interrupt>\n");
printk(" lock(");
__print_lock_name(safe_class);
printk(");\n");
@@ -1487,6 +1495,8 @@ print_bad_irq_dependency(struct task_struct *curr,
enum lock_usage_bit bit2,
const char *irqclass)
{
+ int reclaim = strncmp(irqclass, "RECLAIM", 7) == 0;
+
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return 0;

@@ -1528,7 +1538,7 @@ print_bad_irq_dependency(struct task_struct *curr,

printk("\nother info that might help us debug this:\n\n");
print_irq_lock_scenario(backwards_entry, forwards_entry,
- hlock_class(prev), hlock_class(next));
+ hlock_class(prev), hlock_class(next), reclaim);

lockdep_print_held_locks(curr);

@@ -2200,7 +2210,7 @@ static void check_chain_key(struct task_struct *curr)
}

static void
-print_usage_bug_scenario(struct held_lock *lock)
+print_usage_bug_scenario(struct held_lock *lock, enum lock_usage_bit new_bit)
{
struct lock_class *class = hlock_class(lock);

@@ -2210,7 +2220,11 @@ print_usage_bug_scenario(struct held_lock *lock)
printk(" lock(");
__print_lock_name(class);
printk(");\n");
- printk(" <Interrupt>\n");
+ if (new_bit == LOCK_USED_IN_RECLAIM_FS ||
+ new_bit == LOCK_USED_IN_RECLAIM_FS_READ)
+ printk(" <Memory allocation/reclaim>\n");
+ else
+ printk(" <Interrupt>\n");
printk(" lock(");
__print_lock_name(class);
printk(");\n");
@@ -2246,7 +2260,7 @@ print_usage_bug(struct task_struct *curr, struct held_lock *this,

print_irqtrace_events(curr);
printk("\nother info that might help us debug this:\n");
- print_usage_bug_scenario(this);
+ print_usage_bug_scenario(this, new_bit);

lockdep_print_held_locks(curr);

@@ -2285,13 +2299,17 @@ print_irq_inversion_bug(struct task_struct *curr,
struct lock_list *entry = other;
struct lock_list *middle = NULL;
int depth;
+ int reclaim = strncmp(irqclass, "RECLAIM", 7) == 0;

if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return 0;

printk("\n");
printk("=========================================================\n");
- printk("[ INFO: possible irq lock inversion dependency detected ]\n");
+ if (reclaim)
+ printk("[ INFO: possible memory reclaim lock inversion dependency detected ]\n");
+ else
+ printk("[ INFO: possible irq lock inversion dependency detected ]\n");
print_kernel_ident();
printk("---------------------------------------------------------\n");
printk("%s/%d just changed the state of lock:\n",
@@ -2302,6 +2320,9 @@ print_irq_inversion_bug(struct task_struct *curr,
else
printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
print_lock_name(other->class);
+ if (reclaim)
+ printk("\n\nand memory reclaim could create inverse lock ordering between them.\n\n");
+ else
printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");

printk("\nother info that might help us debug this:\n");
@@ -2319,10 +2340,10 @@ print_irq_inversion_bug(struct task_struct *curr,
} while (entry && entry != root && (depth >= 0));
if (forwards)
print_irq_lock_scenario(root, other,
- middle ? middle->class : root->class, other->class);
+ middle ? middle->class : root->class, other->class, reclaim);
else
print_irq_lock_scenario(other, root,
- middle ? middle->class : other->class, root->class);
+ middle ? middle->class : other->class, root->class, reclaim);

lockdep_print_held_locks(curr);