linux-kernel - Re: [locking/lockdep] 383776fa75: INFO: trying to register non-static key.

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Message-ID: <20170317134109.e7qmjwpryelpbgz2@hirez.programming.kicks-ass.net>
Date:   Fri, 17 Mar 2017 14:41:09 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     kernel test robot <fengguang.wu@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>, LKP <lkp@...org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, wfg@...ux.intel.com
Subject: Re: [locking/lockdep] 383776fa75:  INFO: trying to register
 non-static key.

On Fri, Mar 17, 2017 at 02:07:05AM +0800, kernel test robot wrote:

>     locking/lockdep: Handle statically initialized PER_CPU locks properly

> [   11.712266] INFO: trying to register non-static key.

Blergh; so the problem is that when we assign can_addr to lock->key, we
can, upon using a different subclass, reach static_obj(lock->key), which
will fail on the can_addr.

One way to fix this would be to redefine the canonical address as the
per-cpu address for a specific cpu; the below hard codes cpu0, but I'm
not sure we want to rely on cpu0 being a valid cpu.


---
diff --git a/kernel/module.c b/kernel/module.c
index 5ef618133849..bdd9d62ce08c 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -682,8 +682,10 @@ bool __is_module_percpu_address(unsigned long addr, unsigned long *can_addr)
 			void *va = (void *)addr;
 
 			if (va >= start && va < start + mod->percpu_size) {
-				if (can_addr)
+				if (can_addr) {
 					*can_addr = (unsigned long) (va - start);
+					*can_addr += (unsigned long)per_cpu_ptr(mod->percpu, 0);
+				}
 				preempt_enable();
 				return true;
 			}
diff --git a/mm/percpu.c b/mm/percpu.c
index e30c995f2b7b..a5d7b7477888 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1296,8 +1296,10 @@ bool __is_kernel_percpu_address(unsigned long addr, unsigned long *can_addr)
 		void *va = (void *)addr;
 
 		if (va >= start && va < start + static_size) {
-			if (can_addr)
+			if (can_addr) {
 				*can_addr = (unsigned long) (va - start);
+				*can_addr += (unsigned long)per_cpu_ptr(base, 0);
+			}
 			return true;
 		}
 	}