linux-kernel - [tip:locking/core] lockdep: Fix per-cpu static objects

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Date:   Sun, 26 Mar 2017 02:35:58 -0700
From:   tip-bot for Peter Zijlstra <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     fengguang.wu@...el.com, mingo@...nel.org, bp@...e.de,
        hpa@...or.com, bigeasy@...utronix.de, linux-kernel@...r.kernel.org,
        peterz@...radead.org, lkp@...org, tglx@...utronix.de
Subject: [tip:locking/core] lockdep: Fix per-cpu static objects

Commit-ID:  4ef9ea9524c0015e551d062ac75ab9fd04365277
Gitweb:     http://git.kernel.org/tip/4ef9ea9524c0015e551d062ac75ab9fd04365277
Author:     Peter Zijlstra <peterz@...radead.org>
AuthorDate: Mon, 20 Mar 2017 12:26:55 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sun, 26 Mar 2017 11:27:42 +0200

lockdep: Fix per-cpu static objects

Since commit 383776fa7527 ("locking/lockdep: Handle statically initialized
PER_CPU locks properly") we try to collapse per-cpu locks into a single
class by giving them all the same key. For this key we choose the canonical
address of the per-cpu object, which would be the offset into the per-cpu
area.

This has two problems:

 - there is a case where we run !0 lock->key through static_obj() and
   expect this to pass; it doesn't for canonical pointers.

 - 0 is a valid canonical address.

Cure both issues by redefining the canonical address as the address of the
per-cpu variable on the boot CPU.

Since I didn't want to rely on CPU0 being the boot-cpu, or even existing at
all, track the boot CPU in a variable.

Fixes: 383776fa7527 ("locking/lockdep: Handle statically initialized PER_CPU locks properly")
Reported-by: kernel test robot <fengguang.wu@...el.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Tested-by: Borislav Petkov <bp@...e.de>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-mm@...ck.org
Cc: wfg@...ux.intel.com
Cc: kernel test robot <fengguang.wu@...el.com>
Cc: LKP <lkp@...org>
Link: http://lkml.kernel.org/r/20170320114108.kbvcsuepem45j5cr@hirez.programming.kicks-ass.net
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 include/linux/smp.h | 12 ++++++++++++
 kernel/cpu.c        |  6 ++++++
 kernel/module.c     |  5 ++++-
 mm/percpu.c         |  5 ++++-
 4 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 8e0cb7a..8d41185 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -120,6 +120,13 @@ extern unsigned int setup_max_cpus;
 extern void __init setup_nr_cpu_ids(void);
 extern void __init smp_init(void);
 
+extern int __boot_cpu_id;
+
+static inline int boot_cpu_id(void)
+{
+	return __boot_cpu_id;
+}
+
 #else /* !SMP */
 
 static inline void smp_send_stop(void) { }
@@ -158,6 +165,11 @@ static inline void smp_init(void) { up_late_init(); }
 static inline void smp_init(void) { }
 #endif
 
+static inline int boot_cpu_id(void)
+{
+	return 0;
+}
+
 #endif /* !SMP */
 
 /*
diff --git a/kernel/cpu.c b/kernel/cpu.c
index f7c0632..a795725 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1125,6 +1125,8 @@ core_initcall(cpu_hotplug_pm_sync_init);
 
 #endif /* CONFIG_PM_SLEEP_SMP */
 
+int __boot_cpu_id;
+
 #endif /* CONFIG_SMP */
 
 /* Boot processor state steps */
@@ -1815,6 +1817,10 @@ void __init boot_cpu_init(void)
 	set_cpu_active(cpu, true);
 	set_cpu_present(cpu, true);
 	set_cpu_possible(cpu, true);
+
+#ifdef CONFIG_SMP
+	__boot_cpu_id = cpu;
+#endif
 }
 
 /*
diff --git a/kernel/module.c b/kernel/module.c
index 5ef6181..043ca86 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -682,8 +682,11 @@ 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, boot_cpu_id());
+				}
 				preempt_enable();
 				return true;
 			}
diff --git a/mm/percpu.c b/mm/percpu.c
index 7d3b728..c95b475 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1293,8 +1293,11 @@ 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, boot_cpu_id());
+			}
 			return true;
 		}
 	}