From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E829F4FDA5A; Wed, 30 Sep 2026 16:17:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790785054; cv=none; b=bju27YqvRgW+rM/P08BDubTPiJrddXGZ4pz4iS9JtTNkabJ2AlDd/TJtMc+HzeZDtuzjJg0ro3hVJP60avg3QOuyoXkmujzEupiuFx+1Lih8KHB6q6DHvaW+gvRr3gHkza7p6Ivh1LH5tRMQmnEdTKdwljAutdSBtBvjLteE+ao= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790785054; c=relaxed/simple; bh=bw4G6Ys1ML2TKQv8SYPQOcPY3Atu08hc2ePFlLlOKyQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rMOqqTqKop7fpn6YoxmwSkk7mHcHYv+jByK5+8SH6yCzZ4YVmlZ0GPKrSGKhfutJ3eYwthw9coDAorJPXtOdWVEL28Evuvii2TqkljUUoaRiMPRHLR6VSWWEAtgx47JXRst/qilzPCO4m0RJqnc7Mn67HQjVXTRYfEJL24p0jEM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=kfhHeO18; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="kfhHeO18" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A61281F000FF; Wed, 30 Sep 2026 16:17:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790785045; bh=aTDC8ZLmkO3DkJ9Zkdj4ZDPfQsfreNYnk1GKRm5tl+o=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=kfhHeO18OPbrWEvl4fNWUhDOOQp9ObBjeiDEOVjX5LL/9akW/ozkYhRfjacyq5iKW HWI3ZEw0v3AOsyi38+7KKxbs4uQ8i63ZD8wSjgh9miUbrO02rsL2QuUNVy79GbQsCT fWjPmL9SKsz7OLUDqyCYNNCrdrQkakIKMO3a8bRY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kent Overstreet , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 6.1 370/982] lockdep: Add lock_set_cmp_fn() annotation Date: Wed, 30 Sep 2026 17:18:26 +0200 Message-ID: <20260930152424.758899953@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152416.775402466@linuxfoundation.org> References: <20260930152416.775402466@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kent Overstreet [ Upstream commit eb1cfd09f788e39948a82be8063e54e40dd018d9 ] This implements a new interface to lockdep, lock_set_cmp_fn(), for defining a custom ordering when taking multiple locks of the same class. This is an alternative to subclasses, but can not fully replace them since subclasses allow lock hierarchies with other clasees inter-twined, while this relies on pure class nesting. Specifically, if A is our nesting class then: A/0 <- B <- A/1 Would be a valid lock order with subclasses (each subclass really is a full class from the validation PoV) but not with this annotation, which requires all nesting to be consecutive. Example output: | ============================================ | 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 [peterz: extended changelog] Signed-off-by: Kent Overstreet Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230509195847.1745548-1-kent.overstreet@linux.dev Stable-dep-of: 02c6be7d675b ("locking/lockdep: Invalidate stale class_cache entries for zapped classes") Signed-off-by: Sasha Levin --- include/linux/lockdep.h | 8 +++ include/linux/lockdep_types.h | 8 +++ kernel/locking/lockdep.c | 118 +++++++++++++++++++++++++--------- 3 files changed, 103 insertions(+), 31 deletions(-) diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index c077aa9b16503..7eee13aef36ec 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -447,6 +447,14 @@ extern int lockdep_is_held(const void *); #endif /* !LOCKDEP */ +#ifdef CONFIG_PROVE_LOCKING +void lockdep_set_lock_cmp_fn(struct lockdep_map *, lock_cmp_fn, lock_print_fn); + +#define lock_set_cmp_fn(lock, ...) lockdep_set_lock_cmp_fn(&(lock)->dep_map, __VA_ARGS__) +#else +#define lock_set_cmp_fn(lock, ...) do { } while (0) +#endif + enum xhlock_context_t { XHLOCK_HARD, XHLOCK_SOFT, diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h index 59f4fb1626ea6..2ebc323d345ae 100644 --- a/include/linux/lockdep_types.h +++ b/include/linux/lockdep_types.h @@ -85,6 +85,11 @@ struct lock_trace; #define LOCKSTAT_POINTS 4 +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. * reinit_class() zeroes the key member and all subsequent members. @@ -110,6 +115,9 @@ struct lock_class { struct list_head locks_after, locks_before; 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 2a5b17f855c8a..b16e699cee9fe 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -709,7 +709,7 @@ 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; @@ -724,17 +724,19 @@ 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); @@ -772,7 +774,7 @@ 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); } @@ -1860,7 +1862,7 @@ 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); } @@ -1891,11 +1893,11 @@ 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"); } @@ -1906,13 +1908,13 @@ print_circular_lock_scenario(struct held_lock *src, printk(" rlock("); else 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"); if (src_read != 0) printk(" rlock("); @@ -1920,7 +1922,7 @@ print_circular_lock_scenario(struct held_lock *src, printk(" sync("); else printk(" lock("); - __print_lock_name(source); + __print_lock_name(src, source); printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n"); } @@ -2146,6 +2148,8 @@ check_path(struct held_lock *target, struct lock_list *src_entry, return ret; } +static void print_deadlock_bug(struct task_struct *, struct held_lock *, struct held_lock *); + /* * Prove that the dependency graph starting at can not * lead to . If it can, there is a circle when adding @@ -2177,7 +2181,10 @@ check_noncircular(struct held_lock *src, struct held_lock *target, *trace = save_trace(); } - print_circular_bug(&src_entry, target_entry, src, target); + if (src->class_idx == target->class_idx) + print_deadlock_bug(current, src, target); + else + print_circular_bug(&src_entry, target_entry, src, target); } return ret; @@ -2338,7 +2345,7 @@ 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 @@ -2520,11 +2527,11 @@ 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"); } @@ -2532,18 +2539,18 @@ 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(" \n"); printk(" lock("); - __print_lock_name(safe_class); + __print_lock_name(NULL, safe_class); printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n"); } @@ -2580,20 +2587,20 @@ 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("..."); @@ -2963,10 +2970,10 @@ 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"); @@ -2976,6 +2983,8 @@ static void print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, struct held_lock *next) { + struct lock_class *class = hlock_class(prev); + if (!debug_locks_off_graph_unlock() || debug_locks_silent) return; @@ -2990,6 +2999,11 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, pr_warn("\nbut task is already holding lock:\n"); print_lock(prev); + if (class->cmp_fn) { + pr_warn("and the lock comparison function returns %i:\n", + class->cmp_fn(prev->instance, next->instance)); + } + pr_warn("\nother info that might help us debug this:\n"); print_deadlock_scenario(next, prev); lockdep_print_held_locks(curr); @@ -3011,6 +3025,7 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, static int check_deadlock(struct task_struct *curr, struct held_lock *next) { + struct lock_class *class; struct held_lock *prev; struct held_lock *nest = NULL; int i; @@ -3031,6 +3046,12 @@ check_deadlock(struct task_struct *curr, struct held_lock *next) if ((next->read == 2) && prev->read) continue; + class = hlock_class(prev); + + if (class->cmp_fn && + class->cmp_fn(prev->instance, next->instance) < 0) + continue; + /* * We're holding the nest_lock, which serializes this lock's * nesting behaviour. @@ -3092,6 +3113,14 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, return 2; } + if (prev->class_idx == next->class_idx) { + struct lock_class *class = hlock_class(prev); + + if (class->cmp_fn && + class->cmp_fn(prev->instance, next->instance) < 0) + return 2; + } + /* * Prove that the new -> dependency would not * create a circular dependency in the graph. (We do this by @@ -3569,7 +3598,7 @@ static void print_chain_keys_chain(struct lock_chain *chain) hlock_id = chain_hlocks[chain->base + i]; chain_key = print_chain_key_iteration(hlock_id, chain_key); - print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id)); + print_lock_name(NULL, lock_classes + chain_hlock_class_idx(hlock_id)); printk("\n"); } } @@ -3926,11 +3955,11 @@ 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(" \n"); printk(" lock("); - __print_lock_name(class); + __print_lock_name(lock, class); printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n"); } @@ -4016,7 +4045,7 @@ 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"); @@ -4889,6 +4918,33 @@ EXPORT_SYMBOL_GPL(lockdep_init_map_type); struct lock_class_key __lockdep_no_validate__; EXPORT_SYMBOL_GPL(__lockdep_no_validate__); +#ifdef CONFIG_PROVE_LOCKING +void lockdep_set_lock_cmp_fn(struct lockdep_map *lock, lock_cmp_fn cmp_fn, + lock_print_fn print_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); + + if (class) { + WARN_ON(class->cmp_fn && class->cmp_fn != cmp_fn); + WARN_ON(class->print_fn && class->print_fn != print_fn); + + class->cmp_fn = cmp_fn; + class->print_fn = print_fn; + } + + lockdep_recursion_finish(); + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lockdep_set_lock_cmp_fn); +#endif + static void print_lock_nested_lock_not_held(struct task_struct *curr, struct held_lock *hlock) -- 2.53.0