Subject: Re: [PATCH 1/8] percpu: add __percpu sparse annotations to core kernel subsystems

From: "Paul E. McKenney" <[email-masked]>
Date: Sun, 31 Jan 2010 03:42:26 -0800

On Tue, Jan 26, 2010 at 12:22:08AM +0900, Tejun Heo wrote:
> Add __percpu sparse annotations to core subsystems.
> 
> These annotations are to make sparse consider percpu variables to be
> in a different address space and warn if accessed without going
> through percpu accessors.  This patch doesn't affect normal builds.

The RCU pieces look fine to me.

Acked-by: Paul E. McKenney <[email-masked]>

> Signed-off-by: Tejun Heo <[email-masked]>
> Cc: Jens Axboe <[email-masked]>
> Cc: [email-masked]
> Cc: Rusty Russell <[email-masked]>
> Cc: Dipankar Sarma <[email-masked]>
> Cc: "Paul E. McKenney" <[email-masked]>
> Cc: Peter Zijlstra <[email-masked]>
> Cc: Andrew Morton <[email-masked]>
> Cc: Eric Biederman <[email-masked]>
> ---
>  include/linux/blktrace_api.h   |    4 ++--
>  include/linux/genhd.h          |    2 +-
>  include/linux/kexec.h          |    2 +-
>  include/linux/mmzone.h         |    2 +-
>  include/linux/module.h         |    2 +-
>  include/linux/percpu_counter.h |    2 +-
>  include/linux/srcu.h           |    2 +-
>  kernel/kexec.c                 |    2 +-
>  kernel/sched.c                 |    4 ++--
>  kernel/stop_machine.c          |    2 +-
>  mm/percpu.c                    |   18 ++++++++++--------
>  11 files changed, 22 insertions(+), 20 deletions(-)
> 
> diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
> index 3b73b99..416bf62 100644
> --- a/include/linux/blktrace_api.h
> +++ b/include/linux/blktrace_api.h
> @@ -150,8 +150,8 @@ struct blk_user_trace_setup {
>  struct blk_trace {
>  	int trace_state;
>  	struct rchan *rchan;
> -	unsigned long *sequence;
> -	unsigned char *msg_data;
> +	unsigned long __percpu *sequence;
> +	unsigned char __percpu *msg_data;
>  	u16 act_mask;
>  	u64 start_lba;
>  	u64 end_lba;
> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
> index 9717081..56b5051 100644
> --- a/include/linux/genhd.h
> +++ b/include/linux/genhd.h
> @@ -101,7 +101,7 @@ struct hd_struct {
>  	unsigned long stamp;
>  	int in_flight[2];
>  #ifdef	CONFIG_SMP
> -	struct disk_stats *dkstats;
> +	struct disk_stats __percpu *dkstats;
>  #else
>  	struct disk_stats dkstats;
>  #endif
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index c356b69..03e8e8d 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -199,7 +199,7 @@ extern struct kimage *kexec_crash_image;
>   */
>  extern struct resource crashk_res;
>  typedef u32 note_buf_t[KEXEC_NOTE_BYTES/4];
> -extern note_buf_t *crash_notes;
> +extern note_buf_t __percpu *crash_notes;
>  extern u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
>  extern size_t vmcoreinfo_size;
>  extern size_t vmcoreinfo_max_size;
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 7874201..41acd4b 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -301,7 +301,7 @@ struct zone {
>  	unsigned long		min_unmapped_pages;
>  	unsigned long		min_slab_pages;
>  #endif
> -	struct per_cpu_pageset	*pageset;
> +	struct per_cpu_pageset __percpu *pageset;
>  	/*
>  	 * free areas of different sizes
>  	 */
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 7e74ae0..dd618eb 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -365,7 +365,7 @@ struct module
> 
>  	struct module_ref {
>  		int count;
> -	} *refptr;
> +	} __percpu *refptr;
>  #endif
> 
>  #ifdef CONFIG_CONSTRUCTORS
> diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h
> index a7684a5..9bd103c 100644
> --- a/include/linux/percpu_counter.h
> +++ b/include/linux/percpu_counter.h
> @@ -21,7 +21,7 @@ struct percpu_counter {
>  #ifdef CONFIG_HOTPLUG_CPU
>  	struct list_head list;	/* All percpu_counters are on a list */
>  #endif
> -	s32 *counters;
> +	s32 __percpu *counters;
>  };
> 
>  extern int percpu_counter_batch;
> diff --git a/include/linux/srcu.h b/include/linux/srcu.h
> index 4765d97..41eedcc 100644
> --- a/include/linux/srcu.h
> +++ b/include/linux/srcu.h
> @@ -33,7 +33,7 @@ struct srcu_struct_array {
> 
>  struct srcu_struct {
>  	int completed;
> -	struct srcu_struct_array *per_cpu_ref;
> +	struct srcu_struct_array __percpu *per_cpu_ref;
>  	struct mutex mutex;
>  };
> 
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index a9a93d9..c769613 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -40,7 +40,7 @@
>  #include <asm/sections.h>
> 
>  /* Per cpu memory for storing cpu states in case of system crash. */
> -note_buf_t* crash_notes;
> +note_buf_t __percpu *crash_notes;
> 
>  /* vmcoreinfo stuff */
>  static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES];
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 4508fe7..512b10f 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -1566,7 +1566,7 @@ static unsigned long cpu_avg_load_per_task(int cpu)
> 
>  #ifdef CONFIG_FAIR_GROUP_SCHED
> 
> -static __read_mostly unsigned long *update_shares_data;
> +static __read_mostly unsigned long __percpu *update_shares_data;
> 
>  static void __set_se_shares(struct sched_entity *se, unsigned long shares);
> 
> @@ -10668,7 +10668,7 @@ struct cgroup_subsys cpu_cgroup_subsys = {
>  struct cpuacct {
>  	struct cgroup_subsys_state css;
>  	/* cpuusage holds pointer to a u64-type object on every cpu */
> -	u64 *cpuusage;
> +	u64 __percpu *cpuusage;
>  	struct percpu_counter cpustat[CPUACCT_STAT_NSTATS];
>  	struct cpuacct *parent;
>  };
> diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
> index 912823e..9bb9fb1 100644
> --- a/kernel/stop_machine.c
> +++ b/kernel/stop_machine.c
> @@ -45,7 +45,7 @@ static int refcount;
>  static struct workqueue_struct *stop_machine_wq;
>  static struct stop_machine_data active, idle;
>  static const struct cpumask *active_cpus;
> -static void *stop_machine_work;
> +static void __percpu *stop_machine_work;
> 
>  static void set_state(enum stopmachine_state newstate)
>  {
> diff --git a/mm/percpu.c b/mm/percpu.c
> index b336638..768419d 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -80,13 +80,15 @@
>  /* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
>  #ifndef __addr_to_pcpu_ptr
>  #define __addr_to_pcpu_ptr(addr)					\
> -	(void *)((unsigned long)(addr) - (unsigned long)pcpu_base_addr	\
> -		 + (unsigned long)__per_cpu_start)
> +	(void __percpu *)((unsigned long)(addr) -			\
> +			  (unsigned long)pcpu_base_addr	+		\
> +			  (unsigned long)__per_cpu_start)
>  #endif
>  #ifndef __pcpu_ptr_to_addr
>  #define __pcpu_ptr_to_addr(ptr)						\
> -	(void *)((unsigned long)(ptr) + (unsigned long)pcpu_base_addr	\
> -		 - (unsigned long)__per_cpu_start)
> +	(void __force *)((unsigned long)(ptr) +				\
> +			 (unsigned long)pcpu_base_addr -		\
> +			 (unsigned long)__per_cpu_start)
>  #endif
> 
>  struct pcpu_chunk {
> @@ -1065,7 +1067,7 @@ static struct pcpu_chunk *alloc_pcpu_chunk(void)
>   * RETURNS:
>   * Percpu pointer to the allocated area on success, NULL on failure.
>   */
> -static void *pcpu_alloc(size_t size, size_t align, bool reserved)
> +static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved)
>  {
>  	static int warn_limit = 10;
>  	struct pcpu_chunk *chunk;
> @@ -1194,7 +1196,7 @@ fail_unlock_mutex:
>   * RETURNS:
>   * Percpu pointer to the allocated area on success, NULL on failure.
>   */
> -void *__alloc_percpu(size_t size, size_t align)
> +void __percpu *__alloc_percpu(size_t size, size_t align)
>  {
>  	return pcpu_alloc(size, align, false);
>  }
> @@ -1215,7 +1217,7 @@ EXPORT_SYMBOL_GPL(__alloc_percpu);
>   * RETURNS:
>   * Percpu pointer to the allocated area on success, NULL on failure.
>   */
> -void *__alloc_reserved_percpu(size_t size, size_t align)
> +void __percpu *__alloc_reserved_percpu(size_t size, size_t align)
>  {
>  	return pcpu_alloc(size, align, true);
>  }
> @@ -1267,7 +1269,7 @@ static void pcpu_reclaim(struct work_struct *work)
>   * CONTEXT:
>   * Can be called from atomic context.
>   */
> -void free_percpu(void *ptr)
> +void free_percpu(void __percpu *ptr)
>  {
>  	void *addr;
>  	struct pcpu_chunk *chunk;
> -- 
> 1.6.4.2
> 

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