From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752380AbdIFIci (ORCPT ); Wed, 6 Sep 2017 04:32:38 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:34046 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752042AbdIFIca (ORCPT ); Wed, 6 Sep 2017 04:32:30 -0400 X-Google-Smtp-Source: ADKCNb7mOCG2RRR13xTfeQcXqfIuL7baEvQBPJIQckAxp2LrZgxLtEYAqAzq2WmhVOlJvHUdOEgAdQ== From: Boqun Feng To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Gautham R Shenoy , Byungchul Park , Boqun Feng Subject: [RFC tip/locking v2 08/13] lockdep: Fix recursive read lock related safe->unsafe detection Date: Wed, 6 Sep 2017 16:28:19 +0800 Message-Id: <20170906082824.16078-9-boqun.feng@gmail.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170906082824.16078-1-boqun.feng@gmail.com> References: <20170906082824.16078-1-boqun.feng@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There are four cases for recursive read lock realted deadlocks: (--(X..Y)--> means a strong dependency path starts with a --(X*)--> dependency and ends with a --(*Y)-- dependency.) 1. An irq-safe lock L1 has a dependency --(*..*)--> to an irq-unsafe lock L2. 2. An irq-read-safe lock L1 has a dependency --(N..*)--> to an irq-unsafe lock L2. 3. An irq-safe lock L1 has a dependency --(*..N)--> to an irq-read-unsafe lock L2. 4. An irq-read-safe lock L1 has a dependency --(N..N)--> to an irq-read-unsafe lock L2. The current check_usage() only checks 1) and 2), so this patch adds checks for 3) and 4) and makes sure when find_usage_{back,for}wards find an irq-read-{,un}safe lock, the traverse path should ends at a dependency --(*N)-->. Note when we search backwards, --(*N)--> indicates a real dependency --(N*)-->. Signed-off-by: Boqun Feng --- kernel/locking/lockdep.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 8a09b1a02342..6659b91b70f2 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1505,7 +1505,14 @@ check_redundant(struct lock_list *root, struct held_lock *target, static inline int usage_match(struct lock_list *entry, void *bit) { - return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit); + enum lock_usage_bit ub = (enum lock_usage_bit)bit; + + + if (ub & 1) + return entry->class->usage_mask & (1 << ub) && + !entry->is_rr; + else + return entry->class->usage_mask & (1 << ub); } @@ -1816,6 +1823,10 @@ static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, exclusive_bit(bit), state_name(bit))) return 0; + if (!check_usage(curr, prev, next, bit, + exclusive_bit(bit) + 1, state_name(bit))) + return 0; + bit++; /* _READ */ /* @@ -1828,6 +1839,10 @@ static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, exclusive_bit(bit), state_name(bit))) return 0; + if (!check_usage(curr, prev, next, bit, + exclusive_bit(bit) + 1, state_name(bit))) + return 0; + return 1; } -- 2.14.1