From: Peter Zijlstra <peterz@infradead.org>
To: Bart Van Assche <bvanassche@acm.org>
Cc: mingo@redhat.com, tj@kernel.org, johannes.berg@intel.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 22/27] locking/lockdep: Reuse list entries that are no longer in use
Date: Thu, 29 Nov 2018 11:49:02 +0100 [thread overview]
Message-ID: <20181129104902.GH2131@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20181128234325.110011-23-bvanassche@acm.org>
On Wed, Nov 28, 2018 at 03:43:20PM -0800, Bart Van Assche wrote:
> Instead of abandoning elements of list_entries[] that are no longer in
> use, make alloc_list_entry() reuse array elements that have been freed.
> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> index 43327a1dd488..01e55fca7c2c 100644
> --- a/include/linux/lockdep.h
> +++ b/include/linux/lockdep.h
> @@ -183,6 +183,11 @@ static inline void lockdep_copy_map(struct lockdep_map *to,
> struct lock_list {
> /* Entry in locks_after or locks_before. */
> struct list_head lock_order_entry;
> + /*
> + * Entry in all_list_entries when in use and entry in
> + * free_list_entries when not in use.
> + */
> + struct list_head alloc_entry;
> struct lock_class *class;
> struct lock_class *links_to;
> struct stack_trace trace;
> +static LIST_HEAD(all_list_entries);
> +static LIST_HEAD(free_list_entries);
>
> @@ -862,7 +867,10 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
> */
> static struct lock_list *alloc_list_entry(void)
> {
> - if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
> + struct lock_list *e = list_first_entry_or_null(&free_list_entries,
> + typeof(*e), alloc_entry);
> +
> + if (!e) {
> if (!debug_locks_off_graph_unlock())
> return NULL;
>
> @@ -870,7 +878,8 @@ static struct lock_list *alloc_list_entry(void)
> dump_stack();
> return NULL;
> }
> - return list_entries + nr_list_entries++;
> + list_move_tail(&e->alloc_entry, &all_list_entries);
> + return e;
> }
> @@ -4235,19 +4244,19 @@ static void zap_class(struct list_head *zapped_classes,
> struct lock_class *class)
> {
> struct lock_class *links_to;
> + struct lock_list *entry, *tmp;
>
> /*
> * Remove all dependencies this lock is
> * involved in:
> */
> + list_for_each_entry_safe(entry, tmp, &all_list_entries, alloc_entry) {
> if (entry->class != class && entry->links_to != class)
> continue;
> links_to = entry->links_to;
> WARN_ON_ONCE(entry->class == links_to);
> list_del_rcu(&entry->lock_order_entry);
> + list_move(&entry->alloc_entry, &free_list_entries);
> entry->class = NULL;
> entry->links_to = NULL;
> check_free_class(zapped_classes, class);
Hurm.. I'm confused here.
The reason you cannot re-use lock_order_entry for the free list is
because list_del_rcu(), right? But if so, then what ensures the
list_entry is not re-used before it's grace-period?
next prev parent reply other threads:[~2018-11-29 10:49 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-28 23:42 [PATCH 00/27] locking/lockdep: Add support for dynamic keys Bart Van Assche
2018-11-28 23:42 ` [PATCH 01/27] lockdep tests: Display compiler warning and error messages Bart Van Assche
2018-11-28 23:43 ` [PATCH 02/27] lockdep tests: Fix shellcheck warnings Bart Van Assche
2018-11-28 23:43 ` [PATCH 03/27] lockdep tests: Improve testing accuracy Bart Van Assche
2018-11-28 23:43 ` [PATCH 04/27] lockdep tests: Run lockdep tests a second time under Valgrind Bart Van Assche
2018-11-28 23:43 ` [PATCH 05/27] liblockdep: Rename "trywlock" into "trywrlock" Bart Van Assche
2018-11-28 23:43 ` [PATCH 06/27] liblockdep: Add dummy print_irqtrace_events() implementation Bart Van Assche
2018-11-28 23:43 ` [PATCH 07/27] lockdep tests: Test the lockdep_reset_lock() implementation Bart Van Assche
2018-11-28 23:43 ` [PATCH 08/27] locking/lockdep: Declare local symbols static Bart Van Assche
2018-11-28 23:43 ` [PATCH 09/27] locking/lockdep: Inline __lockdep_init_map() Bart Van Assche
2018-11-28 23:43 ` [PATCH 10/27] locking/lockdep: Introduce lock_class_cache_is_registered() Bart Van Assche
2018-11-28 23:43 ` [PATCH 11/27] timekeeping: Assign a name to tk_core.seq.dep_map Bart Van Assche
2018-12-05 10:03 ` [tip:timers/core] timekeeping: Use proper seqcount initializer tip-bot for Bart Van Assche
2018-11-28 23:43 ` [PATCH 12/27] net/core: Assign a name to devnet_rename_seq.dep_map Bart Van Assche
2018-11-29 0:45 ` David Miller
2018-11-28 23:43 ` [PATCH 13/27] locking/lockdep: Complain if a lock object has no name Bart Van Assche
2018-11-28 23:43 ` [PATCH 14/27] locking/lockdep: Remove a superfluous INIT_LIST_HEAD() statement Bart Van Assche
2018-11-28 23:43 ` [PATCH 15/27] locking/lockdep: Make concurrent lockdep_reset_lock() calls safe Bart Van Assche
2018-11-28 23:43 ` [PATCH 16/27] locking/lockdep: Stop using RCU primitives to access all_lock_classes Bart Van Assche
2018-11-28 23:43 ` [PATCH 17/27] locking/lockdep: Make zap_class() remove all matching lock order entries Bart Van Assche
2018-11-28 23:43 ` [PATCH 18/27] locking/lockdep: Reorder struct lock_class members Bart Van Assche
2018-11-28 23:43 ` [PATCH 19/27] locking/lockdep: Retain the class key and name while freeing a lock class Bart Van Assche
2018-11-28 23:43 ` [PATCH 20/27] locking/lockdep: Free lock classes that are no longer in use Bart Van Assche
2018-11-29 10:37 ` Peter Zijlstra
2018-11-28 23:43 ` [PATCH 21/27] locking/lockdep: Rename lock_list.entry into lock_list.lock_order_entry Bart Van Assche
2018-11-28 23:43 ` [PATCH 22/27] locking/lockdep: Reuse list entries that are no longer in use Bart Van Assche
2018-11-29 10:49 ` Peter Zijlstra [this message]
2018-11-29 12:01 ` Peter Zijlstra
2018-11-29 16:48 ` Bart Van Assche
2018-12-01 20:24 ` Peter Zijlstra
2018-12-03 16:40 ` Bart Van Assche
2018-12-03 17:32 ` Peter Zijlstra
2018-12-03 18:16 ` Bart Van Assche
2018-12-04 8:14 ` Peter Zijlstra
2018-12-04 16:08 ` Bart Van Assche
2018-11-28 23:43 ` [PATCH 23/27] locking/lockdep: Check data structure consistency Bart Van Assche
2018-11-29 12:30 ` Peter Zijlstra
2018-11-29 16:50 ` Bart Van Assche
2018-11-29 16:59 ` Peter Zijlstra
2018-11-28 23:43 ` [PATCH 24/27] locking/lockdep: Introduce __lockdep_free_key_range() Bart Van Assche
2018-11-29 10:00 ` Peter Zijlstra
2018-11-28 23:43 ` [PATCH 25/27] locking/lockdep: Add support for dynamic keys Bart Van Assche
2018-11-29 10:10 ` Peter Zijlstra
2018-12-03 17:07 ` Bart Van Assche
2018-12-03 17:31 ` Peter Zijlstra
2018-11-29 12:04 ` Peter Zijlstra
2018-11-29 16:59 ` Bart Van Assche
2018-11-28 23:43 ` [PATCH 26/27] kernel/workqueue: Use dynamic lockdep keys for workqueues Bart Van Assche
2018-11-28 23:43 ` [PATCH 27/27] lockdep tests: Test dynamic key registration Bart Van Assche
2018-11-29 12:31 ` [PATCH 00/27] locking/lockdep: Add support for dynamic keys Peter Zijlstra
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