From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758171AbeAIOh0 (ORCPT + 1 other); Tue, 9 Jan 2018 09:37:26 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:36919 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757978AbeAIOhV (ORCPT ); Tue, 9 Jan 2018 09:37:21 -0500 X-Google-Smtp-Source: ACJfBosxYW6IVmpmqZ4wOT12gXoE3NqOFurzxNZU2IuGGmRcfLU7Ob+MlpA6Zb4UrefGH/zX0GUB1w== X-ME-Sender: From: Boqun Feng To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar , Boqun Feng Subject: [RFC tip/locking/lockdep v4 08/17] lockdep: Fix recursive read lock related safe->unsafe detection Date: Tue, 9 Jan 2018 22:38:51 +0800 Message-Id: <20180109143900.27475-9-boqun.feng@gmail.com> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20180109143900.27475-1-boqun.feng@gmail.com> References: <20180109143900.27475-1-boqun.feng@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: 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 4655219c28c1..c7b1273a044a 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1499,7 +1499,14 @@ 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); } @@ -1810,6 +1817,10 @@ 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 */ /* @@ -1822,6 +1833,10 @@ 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; } -- 2.15.1