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Subject[PATCH RT 1/6] lockdep: Fix per-cpu static objects
Date
4.1.42-rt50-rc1 stable review patch.
If you have any objection to the inclusion of this patch, let me know.

--- 8< --- 8< --- 8< ---
From: Peter Zijlstra <peterz@infradead.org>

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@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Borislav Petkov <bp@suse.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-mm@kvack.org
Cc: wfg@linux.intel.com
Cc: kernel test robot <fengguang.wu@intel.com>
Cc: LKP <lkp@01.org>
Link: http://lkml.kernel.org/r/20170320114108.kbvcsuepem45j5cr@hirez.programming.kicks-ass.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
(cherry picked from commit c9fe9196079f738c89c3ffcdce3fbe142ac3f3c4)
Signed-off-by: Julia Cartwright <julia@ni.com>
---
include/linux/smp.h | 12 ++++++++++++
init/main.c | 8 ++++++++
kernel/module.c | 6 +++++-
mm/percpu.c | 5 ++++-
4 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index e6ab36aeaaab..cbf6836524dc 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 get_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 get_boot_cpu_id(void)
+{
+ return 0;
+}
+
#endif /* !SMP */

/*
diff --git a/init/main.c b/init/main.c
index 0486a8e11fc0..e1bae15a2154 100644
--- a/init/main.c
+++ b/init/main.c
@@ -451,6 +451,10 @@ void __init parse_early_param(void)
* Activate the first processor.
*/

+#ifdef CONFIG_SMP
+int __boot_cpu_id;
+#endif
+
static void __init boot_cpu_init(void)
{
int cpu = smp_processor_id();
@@ -459,6 +463,10 @@ static 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
}

void __init __weak smp_setup_processor_id(void)
diff --git a/kernel/module.c b/kernel/module.c
index a7ac858fd1a1..982c57b2c2a1 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -542,8 +542,12 @@ 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,
+ get_boot_cpu_id());
+ }
preempt_enable();
return true;
}
diff --git a/mm/percpu.c b/mm/percpu.c
index 4146b00bfde7..b41c3960d5fb 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1297,8 +1297,11 @@ 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, get_boot_cpu_id());
+ }
return true;
}
}
--
2.13.1
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