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a263898f62
make randconfig bootup testing found that the cpufreq code
crashes on bootup, if the powernow-k8 driver is enabled and
if maxcpus=1 passed on the boot line to a !CONFIG_HOTPLUG_CPU
kernel.
First lockdep found out that there's an inconsistent unlock
sequence:
=====================================
[ BUG: bad unlock balance detected! ]
-------------------------------------
swapper/1 is trying to release lock (&per_cpu(cpu_policy_rwsem, cpu)) at:
[<ffffffff806ffd8e>] unlock_policy_rwsem_write+0x3c/0x42
but there are no more locks to release!
Call Trace:
[<ffffffff806ffd8e>] unlock_policy_rwsem_write+0x3c/0x42
[<ffffffff80251c29>] print_unlock_inbalance_bug+0x104/0x12c
[<ffffffff80252f3a>] mark_held_locks+0x56/0x94
[<ffffffff806ffd8e>] unlock_policy_rwsem_write+0x3c/0x42
[<ffffffff807008b6>] cpufreq_add_dev+0x2a8/0x5c4
...
then shortly afterwards the cpufreq code crashed on an assert:
------------[ cut here ]------------
kernel BUG at drivers/cpufreq/cpufreq.c:1068!
invalid opcode: 0000 [1] SMP
[...]
Call Trace:
[<ffffffff805145d6>] sysdev_driver_unregister+0x5b/0x91
[<ffffffff806ff520>] cpufreq_register_driver+0x15d/0x1a2
[<ffffffff80cc0596>] powernowk8_init+0x86/0x94
[...]
---[ end trace 1e9219be2b4431de ]---
the bug was caused by maxcpus=1 bootup, which brought up the
secondary core as !cpu_online() but !cpu_is_offline() either,
which on on !CONFIG_HOTPLUG_CPU is always 0 (include/linux/cpu.h):
/* CPUs don't go offline once they're online w/o CONFIG_HOTPLUG_CPU */
static inline int cpu_is_offline(int cpu) { return 0; }
but the cpufreq code uses cpu_online() and cpu_is_offline() in
a mixed way - the low-level drivers use cpu_online(), while
the cpufreq core uses cpu_is_offline(). This opened up the
possibility to add the non-initialized sysdev device of the
secondary core:
cpufreq-core: trying to register driver powernow-k8
cpufreq-core: adding CPU 0
powernow-k8: BIOS error - no PSB or ACPI _PSS objects
cpufreq-core: initialization failed
cpufreq-core: adding CPU 1
cpufreq-core: initialization failed
which then blew up. The fix is to make cpu_is_offline() always
the negation of cpu_online(). With that fix applied the kernel
boots up fine without crashing:
Calling initcall 0xffffffff80cc0510: powernowk8_init+0x0/0x94()
powernow-k8: Found 1 AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ processors (1 cpu cores) (version 2.20.00)
powernow-k8: BIOS error - no PSB or ACPI _PSS objects
initcall 0xffffffff80cc0510: powernowk8_init+0x0/0x94() returned -19.
initcall 0xffffffff80cc0510 ran for 19 msecs: powernowk8_init+0x0/0x94()
Calling initcall 0xffffffff80cc328f: init_lapic_nmi_sysfs+0x0/0x39()
We could fix this by making CPU enumeration aware of max_cpus, but that
would be more fragile IMO, and the cpu_online(cpu) != cpu_is_offline(cpu)
possibility was quite confusing and a continuous source of bugs too.
Most distributions have kernels with CPU hotplug enabled, so this bug
remained hidden for a long time.
Bug forensics:
The broken cpu_is_offline() API variant was introduced via:
commit a59d2e4e6977e7b94e003c96a41f07e96cddc340
Author: Rusty Russell <rusty@rustcorp.com.au>
Date: Mon Mar 8 06:06:03 2004 -0800
[PATCH] minor cleanups for hotplug CPUs
( this predates linux-2.6.git, this commit is available from Thomas's
historic git tree. )
Then 1.5 years later the cpufreq code made use of it:
commit c32b6b8e524d2c337767d312814484d9289550cf
Author: Ashok Raj <ashok.raj@intel.com>
Date: Sun Oct 30 14:59:54 2005 -0800
[PATCH] create and destroy cpufreq sysfs entries based on cpu notifiers
+ if (cpu_is_offline(cpu))
+ return 0;
which is a correct use of the subtly broken new API. v2.6.15 then
shipped with this bug included.
then it took two more years for random-kernel qa to hit it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
139 lines
3.8 KiB
C
139 lines
3.8 KiB
C
/*
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* include/linux/cpu.h - generic cpu definition
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*
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* This is mainly for topological representation. We define the
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* basic 'struct cpu' here, which can be embedded in per-arch
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* definitions of processors.
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*
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* Basic handling of the devices is done in drivers/base/cpu.c
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* and system devices are handled in drivers/base/sys.c.
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*
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* CPUs are exported via sysfs in the class/cpu/devices/
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* directory.
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*
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* Per-cpu interfaces can be implemented using a struct device_interface.
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* See the following for how to do this:
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* - drivers/base/intf.c
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* - Documentation/driver-model/interface.txt
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*/
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#ifndef _LINUX_CPU_H_
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#define _LINUX_CPU_H_
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#include <linux/sysdev.h>
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#include <linux/node.h>
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#include <linux/compiler.h>
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#include <linux/cpumask.h>
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#include <asm/semaphore.h>
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#include <linux/mutex.h>
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struct cpu {
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int node_id; /* The node which contains the CPU */
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int hotpluggable; /* creates sysfs control file if hotpluggable */
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struct sys_device sysdev;
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};
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extern int register_cpu(struct cpu *cpu, int num);
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extern struct sys_device *get_cpu_sysdev(unsigned cpu);
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extern int cpu_add_sysdev_attr(struct sysdev_attribute *attr);
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extern void cpu_remove_sysdev_attr(struct sysdev_attribute *attr);
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extern int cpu_add_sysdev_attr_group(struct attribute_group *attrs);
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extern void cpu_remove_sysdev_attr_group(struct attribute_group *attrs);
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extern int sched_create_sysfs_power_savings_entries(struct sysdev_class *cls);
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#ifdef CONFIG_HOTPLUG_CPU
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extern void unregister_cpu(struct cpu *cpu);
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#endif
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struct notifier_block;
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#ifdef CONFIG_SMP
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/* Need to know about CPUs going up/down? */
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#ifdef CONFIG_HOTPLUG_CPU
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extern int register_cpu_notifier(struct notifier_block *nb);
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extern void unregister_cpu_notifier(struct notifier_block *nb);
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#else
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#ifndef MODULE
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extern int register_cpu_notifier(struct notifier_block *nb);
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#else
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static inline int register_cpu_notifier(struct notifier_block *nb)
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{
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return 0;
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}
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#endif
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static inline void unregister_cpu_notifier(struct notifier_block *nb)
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{
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}
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#endif
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int cpu_up(unsigned int cpu);
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#else
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static inline int register_cpu_notifier(struct notifier_block *nb)
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{
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return 0;
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}
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static inline void unregister_cpu_notifier(struct notifier_block *nb)
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{
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}
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#endif /* CONFIG_SMP */
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extern struct sysdev_class cpu_sysdev_class;
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#ifdef CONFIG_HOTPLUG_CPU
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/* Stop CPUs going up and down. */
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static inline void cpuhotplug_mutex_lock(struct mutex *cpu_hp_mutex)
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{
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mutex_lock(cpu_hp_mutex);
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}
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static inline void cpuhotplug_mutex_unlock(struct mutex *cpu_hp_mutex)
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{
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mutex_unlock(cpu_hp_mutex);
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}
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extern void lock_cpu_hotplug(void);
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extern void unlock_cpu_hotplug(void);
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#define hotcpu_notifier(fn, pri) { \
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static struct notifier_block fn##_nb = \
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{ .notifier_call = fn, .priority = pri }; \
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register_cpu_notifier(&fn##_nb); \
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}
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#define register_hotcpu_notifier(nb) register_cpu_notifier(nb)
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#define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb)
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int cpu_down(unsigned int cpu);
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#else /* CONFIG_HOTPLUG_CPU */
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static inline void cpuhotplug_mutex_lock(struct mutex *cpu_hp_mutex)
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{ }
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static inline void cpuhotplug_mutex_unlock(struct mutex *cpu_hp_mutex)
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{ }
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#define lock_cpu_hotplug() do { } while (0)
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#define unlock_cpu_hotplug() do { } while (0)
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#define hotcpu_notifier(fn, pri) do { (void)(fn); } while (0)
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/* These aren't inline functions due to a GCC bug. */
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#define register_hotcpu_notifier(nb) ({ (void)(nb); 0; })
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#define unregister_hotcpu_notifier(nb) ({ (void)(nb); })
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#endif /* CONFIG_HOTPLUG_CPU */
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#ifdef CONFIG_PM_SLEEP_SMP
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extern int suspend_cpu_hotplug;
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extern int disable_nonboot_cpus(void);
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extern void enable_nonboot_cpus(void);
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#else /* !CONFIG_PM_SLEEP_SMP */
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#define suspend_cpu_hotplug 0
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static inline int disable_nonboot_cpus(void) { return 0; }
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static inline void enable_nonboot_cpus(void) {}
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#endif /* !CONFIG_PM_SLEEP_SMP */
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#endif /* _LINUX_CPU_H_ */
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