linux-kernel - Re: [PATCH 09/11] drivers/char/ipmi: convert stats to use counter

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Date:   Fri, 25 Sep 2020 19:15:10 -0500
From:   Corey Minyard <minyard@....org>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     arnd@...db.de, gregkh@...uxfoundation.org, keescook@...omium.org,
        openipmi-developer@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/11] drivers/char/ipmi: convert stats to use
 counter_atomic32

On Fri, Sep 25, 2020 at 05:47:23PM -0600, Shuah Khan wrote:
> counter_atomic* is introduced to be used when a variable is used as
> a simple counter and doesn't guard object lifetimes. This clearly
> differentiates atomic_t usages that guard object lifetimes.
> 
> counter_atomic* variables will wrap around to 0 when it overflows and
> should not be used to guard resource lifetimes, device usage and
> open counts that control state changes, and pm states.
> 
> atomic_t variables used for stats are atomic counters. Overflow will
> wrap around and reset the stats and no change with the conversion.
> 
> Convert them to use counter_atomic32.
> 
> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>

Reviewed-by: Corey Minyard <cminyard@...sta.com>

I assume for this conversion that the plan is to eliminate atomic_t
completely and convert all atomic counters used for object lifetime to
struct kref?  The new naming is certainly more clear and I'm happy with
this change.

-corey

> ---
>  drivers/char/ipmi/ipmi_msghandler.c | 9 +++++----
>  drivers/char/ipmi/ipmi_si_intf.c    | 9 +++++----
>  2 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> index 737c0b6b24ea..36c0b1be22fb 100644
> --- a/drivers/char/ipmi/ipmi_msghandler.c
> +++ b/drivers/char/ipmi/ipmi_msghandler.c
> @@ -34,6 +34,7 @@
>  #include <linux/uuid.h>
>  #include <linux/nospec.h>
>  #include <linux/vmalloc.h>
> +#include <linux/counters.h>
>  
>  #define IPMI_DRIVER_VERSION "39.2"
>  
> @@ -584,7 +585,7 @@ struct ipmi_smi {
>  	struct ipmi_my_addrinfo addrinfo[IPMI_MAX_CHANNELS];
>  	bool channels_ready;
>  
> -	atomic_t stats[IPMI_NUM_STATS];
> +	struct counter_atomic32 stats[IPMI_NUM_STATS];
>  
>  	/*
>  	 * run_to_completion duplicate of smb_info, smi_info
> @@ -630,9 +631,9 @@ static LIST_HEAD(smi_watchers);
>  static DEFINE_MUTEX(smi_watchers_mutex);
>  
>  #define ipmi_inc_stat(intf, stat) \
> -	atomic_inc(&(intf)->stats[IPMI_STAT_ ## stat])
> +	counter_atomic32_inc(&(intf)->stats[IPMI_STAT_ ## stat])
>  #define ipmi_get_stat(intf, stat) \
> -	((unsigned int) atomic_read(&(intf)->stats[IPMI_STAT_ ## stat]))
> +	((unsigned int) counter_atomic32_read(&(intf)->stats[IPMI_STAT_ ## stat]))
>  
>  static const char * const addr_src_to_str[] = {
>  	"invalid", "hotmod", "hardcoded", "SPMI", "ACPI", "SMBIOS", "PCI",
> @@ -3448,7 +3449,7 @@ int ipmi_add_smi(struct module         *owner,
>  	INIT_LIST_HEAD(&intf->cmd_rcvrs);
>  	init_waitqueue_head(&intf->waitq);
>  	for (i = 0; i < IPMI_NUM_STATS; i++)
> -		atomic_set(&intf->stats[i], 0);
> +		counter_atomic32_set(&intf->stats[i], 0);
>  
>  	mutex_lock(&ipmi_interfaces_mutex);
>  	/* Look for a hole in the numbers. */
> diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
> index 77b8d551ae7f..0909a3461f05 100644
> --- a/drivers/char/ipmi/ipmi_si_intf.c
> +++ b/drivers/char/ipmi/ipmi_si_intf.c
> @@ -43,6 +43,7 @@
>  #include "ipmi_si_sm.h"
>  #include <linux/string.h>
>  #include <linux/ctype.h>
> +#include <linux/counters.h>
>  
>  /* Measure times between events in the driver. */
>  #undef DEBUG_TIMING
> @@ -237,7 +238,7 @@ struct smi_info {
>  	bool dev_group_added;
>  
>  	/* Counters and things for the proc filesystem. */
> -	atomic_t stats[SI_NUM_STATS];
> +	struct counter_atomic32 stats[SI_NUM_STATS];
>  
>  	struct task_struct *thread;
>  
> @@ -245,9 +246,9 @@ struct smi_info {
>  };
>  
>  #define smi_inc_stat(smi, stat) \
> -	atomic_inc(&(smi)->stats[SI_STAT_ ## stat])
> +	counter_atomic32_inc(&(smi)->stats[SI_STAT_ ## stat])
>  #define smi_get_stat(smi, stat) \
> -	((unsigned int) atomic_read(&(smi)->stats[SI_STAT_ ## stat]))
> +	((unsigned int) counter_atomic32_read(&(smi)->stats[SI_STAT_ ## stat]))
>  
>  #define IPMI_MAX_INTFS 4
>  static int force_kipmid[IPMI_MAX_INTFS];
> @@ -2013,7 +2014,7 @@ static int try_smi_init(struct smi_info *new_smi)
>  	atomic_set(&new_smi->req_events, 0);
>  	new_smi->run_to_completion = false;
>  	for (i = 0; i < SI_NUM_STATS; i++)
> -		atomic_set(&new_smi->stats[i], 0);
> +		counter_atomic32_set(&new_smi->stats[i], 0);
>  
>  	new_smi->interrupt_disabled = true;
>  	atomic_set(&new_smi->need_watch, 0);
> -- 
> 2.25.1
>