From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753226AbdHJMWA (ORCPT ); Thu, 10 Aug 2017 08:22:00 -0400 Received: from terminus.zytor.com ([65.50.211.136]:47841 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751492AbdHJMV6 (ORCPT ); Thu, 10 Aug 2017 08:21:58 -0400 Date: Thu, 10 Aug 2017 05:18:25 -0700 From: tip-bot for Byungchul Park Message-ID: Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, mingo@kernel.org, tglx@linutronix.de, byungchul.park@lge.com, hpa@zytor.com Reply-To: linux-kernel@vger.kernel.org, mingo@kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, tglx@linutronix.de, hpa@zytor.com, byungchul.park@lge.com In-Reply-To: <1502089981-21272-2-git-send-email-byungchul.park@lge.com> References: <1502089981-21272-2-git-send-email-byungchul.park@lge.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/core] locking/lockdep: Refactor lookup_chain_cache() Git-Commit-ID: 545c23f2e954eb3365629b20ceeef4eadb1ff97f X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 545c23f2e954eb3365629b20ceeef4eadb1ff97f Gitweb: http://git.kernel.org/tip/545c23f2e954eb3365629b20ceeef4eadb1ff97f Author: Byungchul Park AuthorDate: Mon, 7 Aug 2017 16:12:48 +0900 Committer: Ingo Molnar CommitDate: Thu, 10 Aug 2017 12:29:05 +0200 locking/lockdep: Refactor lookup_chain_cache() Currently, lookup_chain_cache() provides both 'lookup' and 'add' functionalities in a function. However, each is useful. So this patch makes lookup_chain_cache() only do 'lookup' functionality and makes add_chain_cahce() only do 'add' functionality. And it's more readable than before. Signed-off-by: Byungchul Park Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: akpm@linux-foundation.org Cc: boqun.feng@gmail.com Cc: kernel-team@lge.com Cc: kirill@shutemov.name Cc: npiggin@gmail.com Cc: walken@google.com Cc: willy@infradead.org Link: http://lkml.kernel.org/r/1502089981-21272-2-git-send-email-byungchul.park@lge.com Signed-off-by: Ingo Molnar --- kernel/locking/lockdep.c | 141 +++++++++++++++++++++++++++++++---------------- 1 file changed, 93 insertions(+), 48 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index b2dd313..e029f2f 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -2151,14 +2151,15 @@ static int check_no_collision(struct task_struct *curr, } /* - * Look up a dependency chain. If the key is not present yet then - * add it and return 1 - in this case the new dependency chain is - * validated. If the key is already hashed, return 0. - * (On return with 1 graph_lock is held.) + * Adds a dependency chain into chain hashtable. And must be called with + * graph_lock held. + * + * Return 0 if fail, and graph_lock is released. + * Return 1 if succeed, with graph_lock held. */ -static inline int lookup_chain_cache(struct task_struct *curr, - struct held_lock *hlock, - u64 chain_key) +static inline int add_chain_cache(struct task_struct *curr, + struct held_lock *hlock, + u64 chain_key) { struct lock_class *class = hlock_class(hlock); struct hlist_head *hash_head = chainhashentry(chain_key); @@ -2166,49 +2167,18 @@ static inline int lookup_chain_cache(struct task_struct *curr, int i, j; /* + * Allocate a new chain entry from the static array, and add + * it to the hash: + */ + + /* * We might need to take the graph lock, ensure we've got IRQs * disabled to make this an IRQ-safe lock.. for recursion reasons * lockdep won't complain about its own locking errors. */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return 0; - /* - * We can walk it lock-free, because entries only get added - * to the hash: - */ - hlist_for_each_entry_rcu(chain, hash_head, entry) { - if (chain->chain_key == chain_key) { -cache_hit: - debug_atomic_inc(chain_lookup_hits); - if (!check_no_collision(curr, hlock, chain)) - return 0; - if (very_verbose(class)) - printk("\nhash chain already cached, key: " - "%016Lx tail class: [%p] %s\n", - (unsigned long long)chain_key, - class->key, class->name); - return 0; - } - } - if (very_verbose(class)) - printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n", - (unsigned long long)chain_key, class->key, class->name); - /* - * Allocate a new chain entry from the static array, and add - * it to the hash: - */ - if (!graph_lock()) - return 0; - /* - * We have to walk the chain again locked - to avoid duplicates: - */ - hlist_for_each_entry(chain, hash_head, entry) { - if (chain->chain_key == chain_key) { - graph_unlock(); - goto cache_hit; - } - } if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) { if (!debug_locks_off_graph_unlock()) return 0; @@ -2260,6 +2230,78 @@ cache_hit: return 1; } +/* + * Look up a dependency chain. + */ +static inline struct lock_chain *lookup_chain_cache(u64 chain_key) +{ + struct hlist_head *hash_head = chainhashentry(chain_key); + struct lock_chain *chain; + + /* + * We can walk it lock-free, because entries only get added + * to the hash: + */ + hlist_for_each_entry_rcu(chain, hash_head, entry) { + if (chain->chain_key == chain_key) { + debug_atomic_inc(chain_lookup_hits); + return chain; + } + } + return NULL; +} + +/* + * If the key is not present yet in dependency chain cache then + * add it and return 1 - in this case the new dependency chain is + * validated. If the key is already hashed, return 0. + * (On return with 1 graph_lock is held.) + */ +static inline int lookup_chain_cache_add(struct task_struct *curr, + struct held_lock *hlock, + u64 chain_key) +{ + struct lock_class *class = hlock_class(hlock); + struct lock_chain *chain = lookup_chain_cache(chain_key); + + if (chain) { +cache_hit: + if (!check_no_collision(curr, hlock, chain)) + return 0; + + if (very_verbose(class)) { + printk("\nhash chain already cached, key: " + "%016Lx tail class: [%p] %s\n", + (unsigned long long)chain_key, + class->key, class->name); + } + + return 0; + } + + if (very_verbose(class)) { + printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n", + (unsigned long long)chain_key, class->key, class->name); + } + + if (!graph_lock()) + return 0; + + /* + * We have to walk the chain again locked - to avoid duplicates: + */ + chain = lookup_chain_cache(chain_key); + if (chain) { + graph_unlock(); + goto cache_hit; + } + + if (!add_chain_cache(curr, hlock, chain_key)) + return 0; + + return 1; +} + static int validate_chain(struct task_struct *curr, struct lockdep_map *lock, struct held_lock *hlock, int chain_head, u64 chain_key) { @@ -2270,11 +2312,11 @@ static int validate_chain(struct task_struct *curr, struct lockdep_map *lock, * * We look up the chain_key and do the O(N^2) check and update of * the dependencies only if this is a new dependency chain. - * (If lookup_chain_cache() returns with 1 it acquires + * (If lookup_chain_cache_add() return with 1 it acquires * graph_lock for us) */ if (!hlock->trylock && hlock->check && - lookup_chain_cache(curr, hlock, chain_key)) { + lookup_chain_cache_add(curr, hlock, chain_key)) { /* * Check whether last held lock: * @@ -2302,14 +2344,17 @@ static int validate_chain(struct task_struct *curr, struct lockdep_map *lock, * Add dependency only if this lock is not the head * of the chain, and if it's not a secondary read-lock: */ - if (!chain_head && ret != 2) + if (!chain_head && ret != 2) { if (!check_prevs_add(curr, hlock)) return 0; + } + graph_unlock(); - } else - /* after lookup_chain_cache(): */ + } else { + /* after lookup_chain_cache_add(): */ if (unlikely(!debug_locks)) return 0; + } return 1; }