From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 75F45C4360F for ; Tue, 2 Apr 2019 16:03:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 30C8E20840 for ; Tue, 2 Apr 2019 16:03:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220986; bh=Ie5HSVYKOd/M6GEi4wabiS/JbOaS6l6oMMTV4n5zjI0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=upDyTZAg/BfIOLgO1ILCYHQ6V11w2epbafWIjKzyQiSIJEQxT8NGHcaE7671D0F6X DmFiGKoKqFrRdldKyWXXDBdXJ14Ec2QHPrjiOnS22zgUSgkL9RPKUcQ4zA3kJC6Y4u cjjFvG22a2R1c9Q3GLuGaEHOmcHz1FRDZnF+K2Yw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730601AbfDBQDF (ORCPT ); Tue, 2 Apr 2019 12:03:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:42866 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730406AbfDBQC6 (ORCPT ); Tue, 2 Apr 2019 12:02:58 -0400 Received: from lenoir.home (lfbn-1-18527-45.w90-101.abo.wanadoo.fr [90.101.69.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 028C020857; Tue, 2 Apr 2019 16:02:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220978; bh=Ie5HSVYKOd/M6GEi4wabiS/JbOaS6l6oMMTV4n5zjI0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=D6Re52v5g0yRaw4nsHK7tC4h21efYOrTPdu/flhYTaRUTZetXEKZ209x/JwW8TU/8 sV4onn0P++D5eZ1mFULTBoEGsPCVpYkqZXHJAmEOM+XPGcUgJxyjP8ljD9KiK7dG9z FhFaE7JoviESzXXgX1zce+X6l0+cZHmDFOu3pPkY= From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Ingo Molnar , Peter Zijlstra Subject: [PATCH 4/4] locking/lockdep: Test all incompatible scenario at once in check_irq_usage() Date: Tue, 2 Apr 2019 18:02:44 +0200 Message-Id: <20190402160244.32434-5-frederic@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402160244.32434-1-frederic@kernel.org> References: <20190402160244.32434-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org check_prev_add_irq() tests all incompatible scenarios one after the other while adding a lock (@next) to a tree dependency (@prev): LOCK_USED_IN_HARDIRQ vs LOCK_ENABLED_HARDIRQ LOCK_USED_IN_HARDIRQ_READ vs LOCK_ENABLED_HARDIRQ LOCK_USED_IN_SOFTIRQ vs LOCK_ENABLED_SOFTIRQ LOCK_USED_IN_SOFTIRQ_READ vs LOCK_ENABLED_SOFTIRQ Also for these four scenarios, we must at least iterate the @prev backward dependency. Then if it matches the relevant LOCK_USED_* bit, we must also iterate the @next forward dependency. Therefore in the best case we iterate 4 times, in the worst case 8 times. A different approach can let us divide the number of branch iterations by 4: 1) Iterate through @prev backward dependencies and accumulate all the IRQ uses in a single mask. In the best case where the current lock hasn't been used in IRQ, we stop here. 2) Iterate through @next forward dependencies and try to find a lock whose usage is exclusive to the accumulated usages gathered in the previous step. If we find one (call it @lockA), we have found an incompatible use, otherwise we stop here. Only bad locking scenario go further. So a sane verification stop here. 3) Iterate again through @prev backward dependency and find the lock whose usage matches @lockA in term of incompatibility. Call that lock @lockB. 4) Report the incompatible usages of @lockA and @lockB If no incompatible use is found, the verification never goes beyond step 2 which means at most two iterations. The following compares the execution measurements of the function check_prev_add_irq(): Number of calls | Avg (ns) | Stdev (ns) | Total time (ns) ------------------------------------------------------------------------ Mainline 8452 | 2652 | 11962 | 22415143 This patch 8452 | 1518 | 7090 | 12835602 Signed-off-by: Frederic Weisbecker Cc: Ingo Molnar Cc: Peter Zijlstra --- kernel/locking/lockdep.c | 212 ++++++++++++++++++++--------- kernel/locking/lockdep_internals.h | 6 + 2 files changed, 151 insertions(+), 67 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 5e149dd78298..80f33c700314 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1676,6 +1676,14 @@ check_redundant(struct lock_list *root, struct lock_class *target, } #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) + +static inline int usage_accumulate(struct lock_list *entry, void *mask) +{ + *(unsigned long *)mask |= entry->class->usage_mask; + + return 0; +} + /* * Forwards and backwards subgraph searching, for the purposes of * proving that two subgraphs can be connected by a new dependency @@ -1687,8 +1695,6 @@ static inline int usage_match(struct lock_list *entry, void *mask) return entry->class->usage_mask & *(unsigned long *)mask; } - - /* * Find a node in the forwards-direction dependency sub-graph starting * at @root->class that matches @bit. @@ -1922,39 +1928,6 @@ print_bad_irq_dependency(struct task_struct *curr, return 0; } -static int -check_usage(struct task_struct *curr, struct held_lock *prev, - struct held_lock *next, enum lock_usage_bit bit_backwards, - enum lock_usage_bit bit_forwards, const char *irqclass) -{ - int ret; - struct lock_list this, that; - struct lock_list *uninitialized_var(target_entry); - struct lock_list *uninitialized_var(target_entry1); - - this.parent = NULL; - - this.class = hlock_class(prev); - ret = find_usage_backwards(&this, lock_flag(bit_backwards), &target_entry); - if (ret < 0) - return print_bfs_bug(ret); - if (ret == 1) - return ret; - - that.parent = NULL; - that.class = hlock_class(next); - ret = find_usage_forwards(&that, lock_flag(bit_forwards), &target_entry1); - if (ret < 0) - return print_bfs_bug(ret); - if (ret == 1) - return ret; - - return print_bad_irq_dependency(curr, &this, &that, - target_entry, target_entry1, - prev, next, - bit_backwards, bit_forwards, irqclass); -} - static const char *state_names[] = { #define LOCKDEP_STATE(__STATE) \ __stringify(__STATE), @@ -1988,45 +1961,151 @@ static int exclusive_bit(int new_bit) return state | (dir ^ LOCK_USAGE_DIR_MASK); } +static unsigned long exclusive_dir_mask(unsigned long mask) +{ + unsigned long excl; + + /* Invert dir */ + excl = (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK; + excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK; + + return excl; +} + +static unsigned long exclusive_mask(unsigned long mask) +{ + unsigned long excl = exclusive_dir_mask(mask); + + /* Strip read */ + excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK; + excl &= ~LOCKF_IRQ_READ; + + return excl; +} + + +/* + * Retrieve the _possible_ original mask to which @mask is + * exclusive. Ie: this is the opposite of exclusive_mask(). + * Note that 2 possible original bits can match an exclusive + * bit: one has LOCK_USAGE_READ_MASK set, the other has it + * cleared. So both are returned for each exclusive bit. + */ +static unsigned long original_mask(unsigned long mask) +{ + unsigned long excl = exclusive_dir_mask(mask); + + /* Include read in existing usages */ + excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK; + + return excl; +} + +/* + * Find the first pair of bit match between an original + * usage mask and an exclusive usage mask. + */ +static int find_exclusive_match(unsigned long mask, + unsigned long excl_mask, + enum lock_usage_bit *bit, + enum lock_usage_bit *excl_bit) +{ + int fs, nr = 0; + + while ((fs = ffs(mask))) { + int excl; + + nr += fs; + excl = exclusive_bit(nr - 1); + if (excl_mask & lock_flag(excl)) { + *bit = nr - 1; + *excl_bit = excl; + return 0; + } + mask >>= fs - 1; + /* + * Prevent from shifts of sizeof(long) which can + * give unpredictable results. + */ + mask >>= 1; + } + return -1; +} + +/* + * Prove that the new dependency does not connect a hardirq-safe(-read) + * lock with a hardirq-unsafe lock - to achieve this we search + * the backwards-subgraph starting at , and the + * forwards-subgraph starting at : + */ static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, - struct held_lock *next, enum lock_usage_bit bit) + struct held_lock *next) { + unsigned long usage_mask = 0, forward_mask, backward_mask; + enum lock_usage_bit forward_bit = 0, backward_bit = 0; + struct lock_list *uninitialized_var(target_entry1); + struct lock_list *uninitialized_var(target_entry); + struct lock_list this, that; + int ret; + /* - * Prove that the new dependency does not connect a hardirq-safe - * lock with a hardirq-unsafe lock - to achieve this we search - * the backwards-subgraph starting at , and the - * forwards-subgraph starting at : + * Step 1: gather all hard/soft IRQs usages backward in an + * accumulated usage mask. */ - if (!check_usage(curr, prev, next, bit, - exclusive_bit(bit), state_name(bit))) - return 0; + this.parent = NULL; + this.class = hlock_class(prev); + + ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, NULL); + if (ret < 0) + return print_bfs_bug(ret); - bit++; /* _READ */ + usage_mask &= LOCKF_USED_IN_IRQ_ALL; + if (!usage_mask) + return 1; /* - * Prove that the new dependency does not connect a hardirq-safe-read - * lock with a hardirq-unsafe lock - to achieve this we search - * the backwards-subgraph starting at , and the - * forwards-subgraph starting at : + * Step 2: find exclusive uses forward that match the previous + * backward accumulated mask. */ - if (!check_usage(curr, prev, next, bit, - exclusive_bit(bit), state_name(bit))) - return 0; + forward_mask = exclusive_mask(usage_mask); - return 1; -} + that.parent = NULL; + that.class = hlock_class(next); -static int -check_prev_add_irq(struct task_struct *curr, struct held_lock *prev, - struct held_lock *next) -{ -#define LOCKDEP_STATE(__STATE) \ - if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \ - return 0; -#include "lockdep_states.h" -#undef LOCKDEP_STATE + ret = find_usage_forwards(&that, forward_mask, &target_entry1); + if (ret < 0) + return print_bfs_bug(ret); + if (ret == 1) + return ret; + + /* + * Step 3: we found a bad match! Now retrieve a lock from the backward + * list whose usage mask matches the exclusive usage mask from the + * lock found on the forward list. + */ + backward_mask = original_mask(target_entry1->class->usage_mask); + + ret = find_usage_backwards(&this, backward_mask, &target_entry); + if (ret < 0) + return print_bfs_bug(ret); + if (DEBUG_LOCKS_WARN_ON(ret == 1)) + return 1; + + /* + * Step 4: narrow down to a pair of incompatible usage bits + * and report it. + */ + ret = find_exclusive_match(target_entry->class->usage_mask, + target_entry1->class->usage_mask, + &backward_bit, &forward_bit); + if (DEBUG_LOCKS_WARN_ON(ret == -1)) + return 1; - return 1; + return print_bad_irq_dependency(curr, &this, &that, + target_entry, target_entry1, + prev, next, + backward_bit, forward_bit, + state_name(backward_bit)); } static void inc_chains(void) @@ -2043,9 +2122,8 @@ static void inc_chains(void) #else -static inline int -check_prev_add_irq(struct task_struct *curr, struct held_lock *prev, - struct held_lock *next) +static inline int check_irq_usage(struct task_struct *curr, + struct held_lock *prev, struct held_lock *next) { return 1; } @@ -2225,7 +2303,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, else if (unlikely(ret < 0)) return print_bfs_bug(ret); - if (!check_prev_add_irq(curr, prev, next)) + if (!check_irq_usage(curr, prev, next)) return 0; /* diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h index d4c197425f68..d849692f2da7 100644 --- a/kernel/locking/lockdep_internals.h +++ b/kernel/locking/lockdep_internals.h @@ -50,6 +50,12 @@ enum { #define LOCKF_USED_IN_IRQ_READ \ (LOCKF_USED_IN_HARDIRQ_READ | LOCKF_USED_IN_SOFTIRQ_READ) +#define LOCKF_ENABLED_IRQ_ALL (LOCKF_ENABLED_IRQ | LOCKF_ENABLED_IRQ_READ) +#define LOCKF_USED_IN_IRQ_ALL (LOCKF_USED_IN_IRQ | LOCKF_USED_IN_IRQ_READ) + +#define LOCKF_IRQ (LOCKF_ENABLED_IRQ | LOCKF_USED_IN_IRQ) +#define LOCKF_IRQ_READ (LOCKF_ENABLED_IRQ_READ | LOCKF_USED_IN_IRQ_READ) + /* * CONFIG_LOCKDEP_SMALL is defined for sparc. Sparc requires .text, * .data and .bss to fit in required 32MB limit for the kernel. With -- 2.21.0