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([2620:15c:2cd:203:5cdc:422c:7b28:ebb5]) by smtp.gmail.com with ESMTPSA id k38sm29396400pgb.33.2018.12.04.16.06.14 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 04 Dec 2018 16:06:14 -0800 (PST) Message-ID: <1543968373.185366.222.camel@acm.org> Subject: Re: [PATCH v2 21/24] locking/lockdep: Verify whether lock objects are small enough to be used as class keys From: Bart Van Assche To: Waiman Long , mingo@redhat.com Cc: peterz@infradead.org, tj@kernel.org, johannes.berg@intel.com, linux-kernel@vger.kernel.org, Johannes Berg Date: Tue, 04 Dec 2018 16:06:13 -0800 In-Reply-To: <0fbedd8d-6eec-051d-b2fd-5246dc47b477@redhat.com> References: <20181204002833.55452-1-bvanassche@acm.org> <20181204002833.55452-22-bvanassche@acm.org> <8ae6bb3f-ab75-e6f2-adfa-8003366b7410@redhat.com> <1543959553.185366.213.camel@acm.org> <0fbedd8d-6eec-051d-b2fd-5246dc47b477@redhat.com> Content-Type: text/plain; charset="UTF-7" X-Mailer: Evolution 3.26.2-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2018-12-04 at 16:50 -0500, Waiman Long wrote: +AD4 On 12/04/2018 04:39 PM, Bart Van Assche wrote: +AD4 +AD4 On Tue, 2018-12-04 at 16:08 -0500, Waiman Long wrote: +AD4 +AD4 +AD4 On 12/03/2018 07:28 PM, Bart Van Assche wrote: +AD4 +AD4 +AD4 +AD4 Cc: Peter Zijlstra +ADw-peterz+AEA-infradead.org+AD4 +AD4 +AD4 +AD4 +AD4 Cc: Waiman Long +ADw-longman+AEA-redhat.com+AD4 +AD4 +AD4 +AD4 +AD4 Cc: Johannes Berg +ADw-johannes+AEA-sipsolutions.net+AD4 +AD4 +AD4 +AD4 +AD4 Signed-off-by: Bart Van Assche +ADw-bvanassche+AEA-acm.org+AD4 +AD4 +AD4 +AD4 +AD4 --- +AD4 +AD4 +AD4 +AD4 kernel/locking/lockdep.c +AHw 9 +-+-+-+-+-+-+-+-+- +AD4 +AD4 +AD4 +AD4 1 file changed, 9 insertions(+-) +AD4 +AD4 +AD4 +AD4 +AD4 +AD4 +AD4 +AD4 diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c +AD4 +AD4 +AD4 +AD4 index c936fce5b9d7..b4772e5fc176 100644 +AD4 +AD4 +AD4 +AD4 --- a/kernel/locking/lockdep.c +AD4 +AD4 +AD4 +AD4 +-+-+- b/kernel/locking/lockdep.c +AD4 +AD4 +AD4 +AD4 +AEAAQA -727,6 +-727,15 +AEAAQA static bool assign+AF8-lock+AF8-key(struct lockdep+AF8-map +ACo-lock) +AD4 +AD4 +AD4 +AD4 +AHs +AD4 +AD4 +AD4 +AD4 unsigned long can+AF8-addr, addr +AD0 (unsigned long)lock+ADs +AD4 +AD4 +AD4 +AD4 +AD4 +AD4 +AD4 +AD4 +- /+ACo +AD4 +AD4 +AD4 +AD4 +- +ACo lockdep+AF8-free+AF8-key+AF8-range() assumes that struct lock+AF8-class+AF8-key +AD4 +AD4 +AD4 +AD4 +- +ACo objects do not overlap. Since we use the address of lock +AD4 +AD4 +AD4 +AD4 +- +ACo objects as class key for static objects, check whether the +AD4 +AD4 +AD4 +AD4 +- +ACo size of lock+AF8-class+AF8-key objects does not exceed the size of +AD4 +AD4 +AD4 +AD4 +- +ACo the smallest lock object. +AD4 +AD4 +AD4 +AD4 +- +ACo-/ +AD4 +AD4 +AD4 +AD4 +- BUILD+AF8-BUG+AF8-ON(sizeof(struct lock+AF8-class+AF8-key) +AD4 sizeof(raw+AF8-spinlock+AF8-t))+ADs +AD4 +AD4 +AD4 +AD4 +- +AD4 +AD4 +AD4 +AD4 if (+AF8AXw-is+AF8-kernel+AF8-percpu+AF8-address(addr, +ACY-can+AF8-addr)) +AD4 +AD4 +AD4 +AD4 lock-+AD4-key +AD0 (void +ACo)can+AF8-addr+ADs +AD4 +AD4 +AD4 +AD4 else if (+AF8AXw-is+AF8-module+AF8-percpu+AF8-address(addr, +ACY-can+AF8-addr)) +AD4 +AD4 +AD4 +AD4 +AD4 +AD4 I don't understand what this check is for. lock+AF8-class+AF8-key and spinlock +AD4 +AD4 +AD4 are different objects. Their relative size shouldn't matter. +AD4 +AD4 +AD4 +AD4 Peter asked me to add this check. +AD4 +AD4 I haven't finished reviewing all your patches yet. Maybe one of the +AD4 subsequent patches requires this. If that is the case, you should move +AD4 this patch after that. Hi Waiman, The existing (v4.20-rc5) code and the comment I added should be sufficient to understand this patch. Bart.