On Fri, Mar 17, 2017 at 03:41:41PM +0100, Sebastian Andrzej Siewior wrote:
> On 2017-03-17 14:41:09 [+0100], Peter Zijlstra wrote:
> > 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.
>
> This solves two problems: The one reported by the bot. The other thing,
> that is fixed by the patch, is that the first PER-CPU variable built-in
> will return 0 for can_addr and so will the first variable in every
> module. As far as I understand it, this should be unique and having the
> same value for multiple different variables does not look too good :)
> So adding the offset from CPU0 sounds good.
Right; so how about something liek this?
---
Subject: lockdep: Fix per-cpu static objects
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Mon Mar 20 12:26:55 CET 2017
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@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
--- 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_l
static inline void smp_init(void) { }
#endif
+static inline int boot_cpu_id(void)
+{
+ return 0;
+}
+
#endif /* !SMP */
/*
--- 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
}
/*
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -682,8 +682,11 @@ bool __is_module_percpu_address(unsigned
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;
}
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1296,8 +1296,11 @@ bool __is_kernel_percpu_address(unsigned
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;
}
}
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