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Date: Mon, 20 Feb 2023 18:51:59 -0500
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, mingo@...hat.com,
stern@...land.harvard.edu
Subject: Re: [PATCH 1/2] lockdep: lock_set_lock_cmp_fn()
On Mon, Feb 20, 2023 at 04:09:33PM +0100, Peter Zijlstra wrote:
> which is much simpler to work with. Can we improve on this? Give the
> cmp_fn an additinoal optional argument of a string pointer or so to fill
> out with actual details to be printed?
Here you go, example bcache output:
Patch is not as pretty as I'd like because not every path that prints a
lock has held_lock available - but the ones we care about in this
scenario do.
============================================
WARNING: possible recursive locking detected
6.2.0-rc8-00003-g7d81e591ca6a-dirty #15 Not tainted
--------------------------------------------
kworker/14:3/938 is trying to acquire lock:
ffff8880143218c8 (&b->lock l=0 0:2803368){++++}-{3:3}, at: bch_btree_node_get.part.0+0x81/0x2b0
but task is already holding lock:
ffff8880143de8c8 (&b->lock l=1 1048575:9223372036854775807){++++}-{3:3}, at: __bch_btree_map_nodes+0xea/0x1e0
and the lock comparison function returns 1:
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&b->lock l=1 1048575:9223372036854775807);
lock(&b->lock l=0 0:2803368);
*** DEADLOCK ***
May be due to missing lock nesting notation
3 locks held by kworker/14:3/938:
#0: ffff888005ea9d38 ((wq_completion)bcache){+.+.}-{0:0}, at: process_one_work+0x1ec/0x530
#1: ffff8880098c3e70 ((work_completion)(&cl->work)#3){+.+.}-{0:0}, at: process_one_work+0x1ec/0x530
#2: ffff8880143de8c8 (&b->lock l=1 1048575:9223372036854775807){++++}-{3:3}, at: __bch_btree_map_nodes+0xea/0x1e0
-- >8 --
Subject: [PATCH] lockdep: lock_set_print_fn()
This implements a new interface to lockedp, lock_set_print_fn(), for
printing additional information about a lock.
This is intended to be useful with the previous lock_set_cmp_fn(); when
defininig an ordering for locks of a given type, we'll want to print out
information about that lock that's relevant for the ordering we defined.
Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
---
include/linux/lockdep.h | 3 ++
include/linux/lockdep_types.h | 2 +
kernel/locking/lockdep.c | 81 ++++++++++++++++++++++-------------
3 files changed, 57 insertions(+), 29 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 98e0338a74..66d8a5a24e 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -664,10 +664,13 @@ lockdep_rcu_suspicious(const char *file, const int line, const char *s)
#ifdef CONFIG_PROVE_LOCKING
void lockdep_set_lock_cmp_fn(struct lockdep_map *lock, lock_cmp_fn fn);
+void lockdep_set_lock_print_fn(struct lockdep_map *lock, lock_print_fn fn);
#define lock_set_cmp_fn(lock, fn) lockdep_set_lock_cmp_fn(&(lock)->dep_map, fn)
+#define lock_set_print_fn(lock, fn) lockdep_set_lock_print_fn(&(lock)->dep_map, fn)
#else
#define lock_set_cmp_fn(lock, fn) do {} while (0)
+#define lock_set_print_fn(lock, fn) do {} while (0)
#endif
#endif /* __LINUX_LOCKDEP_H */
diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
index 813467dccb..8bf79c4e48 100644
--- a/include/linux/lockdep_types.h
+++ b/include/linux/lockdep_types.h
@@ -87,6 +87,7 @@ struct lock_trace;
struct lockdep_map;
typedef int (*lock_cmp_fn)(const struct lockdep_map *a,
const struct lockdep_map *b);
+typedef void (*lock_print_fn)(const struct lockdep_map *map);
/*
* The lock-class itself. The order of the structure members matters.
@@ -114,6 +115,7 @@ struct lock_class {
const struct lockdep_subclass_key *key;
lock_cmp_fn cmp_fn;
+ lock_print_fn print_fn;
unsigned int subclass;
unsigned int dep_gen_id;
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index b9e759743e..edecd0301b 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -708,7 +708,7 @@ void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
usage[i] = '\0';
}
-static void __print_lock_name(struct lock_class *class)
+static void __print_lock_name(struct held_lock *hlock, struct lock_class *class)
{
char str[KSYM_NAME_LEN];
const char *name;
@@ -723,17 +723,19 @@ static void __print_lock_name(struct lock_class *class)
printk(KERN_CONT "#%d", class->name_version);
if (class->subclass)
printk(KERN_CONT "/%d", class->subclass);
+ if (hlock && class->print_fn)
+ class->print_fn(hlock->instance);
}
}
-static void print_lock_name(struct lock_class *class)
+static void print_lock_name(struct held_lock *hlock, struct lock_class *class)
{
char usage[LOCK_USAGE_CHARS];
get_usage_chars(class, usage);
printk(KERN_CONT " (");
- __print_lock_name(class);
+ __print_lock_name(hlock, class);
printk(KERN_CONT "){%s}-{%d:%d}", usage,
class->wait_type_outer ?: class->wait_type_inner,
class->wait_type_inner);
@@ -771,7 +773,7 @@ static void print_lock(struct held_lock *hlock)
}
printk(KERN_CONT "%px", hlock->instance);
- print_lock_name(lock);
+ print_lock_name(hlock, lock);
printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
}
@@ -1867,7 +1869,7 @@ print_circular_bug_entry(struct lock_list *target, int depth)
if (debug_locks_silent)
return;
printk("\n-> #%u", depth);
- print_lock_name(target->class);
+ print_lock_name(NULL, target->class);
printk(KERN_CONT ":\n");
print_lock_trace(target->trace, 6);
}
@@ -1896,11 +1898,11 @@ print_circular_lock_scenario(struct held_lock *src,
*/
if (parent != source) {
printk("Chain exists of:\n ");
- __print_lock_name(source);
+ __print_lock_name(src, source);
printk(KERN_CONT " --> ");
- __print_lock_name(parent);
+ __print_lock_name(NULL, parent);
printk(KERN_CONT " --> ");
- __print_lock_name(target);
+ __print_lock_name(tgt, target);
printk(KERN_CONT "\n\n");
}
@@ -1908,16 +1910,16 @@ print_circular_lock_scenario(struct held_lock *src,
printk(" CPU0 CPU1\n");
printk(" ---- ----\n");
printk(" lock(");
- __print_lock_name(target);
+ __print_lock_name(tgt, target);
printk(KERN_CONT ");\n");
printk(" lock(");
- __print_lock_name(parent);
+ __print_lock_name(NULL, parent);
printk(KERN_CONT ");\n");
printk(" lock(");
- __print_lock_name(target);
+ __print_lock_name(tgt, target);
printk(KERN_CONT ");\n");
printk(" lock(");
- __print_lock_name(source);
+ __print_lock_name(src, source);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
}
@@ -2335,7 +2337,7 @@ static void print_lock_class_header(struct lock_class *class, int depth)
int bit;
printk("%*s->", depth, "");
- print_lock_name(class);
+ print_lock_name(NULL, class);
#ifdef CONFIG_DEBUG_LOCKDEP
printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
#endif
@@ -2517,11 +2519,11 @@ print_irq_lock_scenario(struct lock_list *safe_entry,
*/
if (middle_class != unsafe_class) {
printk("Chain exists of:\n ");
- __print_lock_name(safe_class);
+ __print_lock_name(NULL, safe_class);
printk(KERN_CONT " --> ");
- __print_lock_name(middle_class);
+ __print_lock_name(NULL, middle_class);
printk(KERN_CONT " --> ");
- __print_lock_name(unsafe_class);
+ __print_lock_name(NULL, unsafe_class);
printk(KERN_CONT "\n\n");
}
@@ -2529,18 +2531,18 @@ print_irq_lock_scenario(struct lock_list *safe_entry,
printk(" CPU0 CPU1\n");
printk(" ---- ----\n");
printk(" lock(");
- __print_lock_name(unsafe_class);
+ __print_lock_name(NULL, unsafe_class);
printk(KERN_CONT ");\n");
printk(" local_irq_disable();\n");
printk(" lock(");
- __print_lock_name(safe_class);
+ __print_lock_name(NULL, safe_class);
printk(KERN_CONT ");\n");
printk(" lock(");
- __print_lock_name(middle_class);
+ __print_lock_name(NULL, middle_class);
printk(KERN_CONT ");\n");
printk(" <Interrupt>\n");
printk(" lock(");
- __print_lock_name(safe_class);
+ __print_lock_name(NULL, safe_class);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
}
@@ -2577,20 +2579,20 @@ print_bad_irq_dependency(struct task_struct *curr,
pr_warn("\nand this task is already holding:\n");
print_lock(prev);
pr_warn("which would create a new lock dependency:\n");
- print_lock_name(hlock_class(prev));
+ print_lock_name(prev, hlock_class(prev));
pr_cont(" ->");
- print_lock_name(hlock_class(next));
+ print_lock_name(next, hlock_class(next));
pr_cont("\n");
pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
irqclass);
- print_lock_name(backwards_entry->class);
+ print_lock_name(NULL, backwards_entry->class);
pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
- print_lock_name(forwards_entry->class);
+ print_lock_name(NULL, forwards_entry->class);
pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
pr_warn("...");
@@ -2960,10 +2962,10 @@ print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
printk(" CPU0\n");
printk(" ----\n");
printk(" lock(");
- __print_lock_name(prev);
+ __print_lock_name(prv, prev);
printk(KERN_CONT ");\n");
printk(" lock(");
- __print_lock_name(next);
+ __print_lock_name(nxt, next);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
printk(" May be due to missing lock nesting notation\n\n");
@@ -3943,11 +3945,11 @@ static void print_usage_bug_scenario(struct held_lock *lock)
printk(" CPU0\n");
printk(" ----\n");
printk(" lock(");
- __print_lock_name(class);
+ __print_lock_name(lock, class);
printk(KERN_CONT ");\n");
printk(" <Interrupt>\n");
printk(" lock(");
- __print_lock_name(class);
+ __print_lock_name(lock, class);
printk(KERN_CONT ");\n");
printk("\n *** DEADLOCK ***\n\n");
}
@@ -4033,7 +4035,7 @@ print_irq_inversion_bug(struct task_struct *curr,
pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
else
pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
- print_lock_name(other->class);
+ print_lock_name(NULL, other->class);
pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
pr_warn("\nother info that might help us debug this:\n");
@@ -6645,4 +6647,25 @@ void lockdep_set_lock_cmp_fn(struct lockdep_map *lock, lock_cmp_fn fn)
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lockdep_set_lock_cmp_fn);
+
+void lockdep_set_lock_print_fn(struct lockdep_map *lock, lock_print_fn fn)
+{
+ struct lock_class *class = lock->class_cache[0];
+ unsigned long flags;
+
+ raw_local_irq_save(flags);
+ lockdep_recursion_inc();
+
+ if (!class)
+ class = register_lock_class(lock, 0, 0);
+
+ WARN_ON(class && class->print_fn && class->print_fn != fn);
+
+ if (class)
+ class->print_fn = fn;
+
+ lockdep_recursion_finish();
+ raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lockdep_set_lock_print_fn);
#endif
--
2.39.2
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