linux-kernel - Re: [PATCH] iwlwifi: pcie: make array prop static, shrinks object size

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Date:   Mon, 11 Jun 2018 22:45:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Colin King <colin.king@...onical.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Intel Linux Wireless <linuxwifi@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S . Miller" <davem@...emloft.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iwlwifi: pcie: make array prop static, shrinks object
 size

On Mon, Jun 11, 2018 at 12:40:55PM -0700, Joe Perches wrote:
> (adding Greg KH)
> 
> On Mon, 2018-06-11 at 18:15 +0100, Colin King wrote:
> > From: Colin Ian King <colin.king@...onical.com>
> > 
> > Don't populate the read-only array 'prop' on the stack but
> > instead make it static. Makes the object code smaller by 20 bytes:
> > 
> > Before:
> >    text    data     bss     dec     hex filename
> >   71659   14614     576   86849   15341 trans.o
> > 
> > After:
> >    text    data     bss     dec     hex filename
> >   71479   14774     576   86829   1532d trans.o
> > 
> > (gcc version 7.3.0 x86_64)
> > 
> > Signed-off-by: Colin Ian King <colin.king@...onical.com>
> > ---
> >  drivers/net/wireless/intel/iwlwifi/pcie/trans.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
> > index 7229991ae70d..c4626ebe5da1 100644
> > --- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
> > +++ b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
> > @@ -1946,7 +1946,7 @@ static void iwl_trans_pcie_removal_wk(struct work_struct *wk)
> >  	struct iwl_trans_pcie_removal *removal =
> >  		container_of(wk, struct iwl_trans_pcie_removal, work);
> >  	struct pci_dev *pdev = removal->pdev;
> > -	char *prop[] = {"EVENT=INACCESSIBLE", NULL};
> > +	static char *prop[] = {"EVENT=INACCESSIBLE", NULL};
> >  
> >  	dev_err(&pdev->dev, "Device gone - attempting removal\n");
> >  	kobject_uevent_env(&pdev->dev.kobj, KOBJ_CHANGE, prop);
> 
> Now what is happening is that prop is being reloaded
> each invocation with the constant addresses of the strings.
> 
> It seems the prototype and function for kobject_uevent_env
> should change as well to avoid this.
> 
> Perhaps this should become:
> ---
>  drivers/net/wireless/intel/iwlwifi/pcie/trans.c | 2 +-
>  include/linux/kobject.h                         | 2 +-
>  lib/kobject_uevent.c                            | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
> index 7229991ae70d..6668a8aad22e 100644
> --- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
> +++ b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
> @@ -1946,7 +1946,7 @@ static void iwl_trans_pcie_removal_wk(struct work_struct *wk)
>  	struct iwl_trans_pcie_removal *removal =
>  		container_of(wk, struct iwl_trans_pcie_removal, work);
>  	struct pci_dev *pdev = removal->pdev;
> -	char *prop[] = {"EVENT=INACCESSIBLE", NULL};
> +	static const char * const prop[] = {"EVENT=INACCESSIBLE", NULL};
>  
>  	dev_err(&pdev->dev, "Device gone - attempting removal\n");
>  	kobject_uevent_env(&pdev->dev.kobj, KOBJ_CHANGE, prop);
> diff --git a/include/linux/kobject.h b/include/linux/kobject.h
> index 7f6f93c3df9c..9f5cf553dd1e 100644
> --- a/include/linux/kobject.h
> +++ b/include/linux/kobject.h
> @@ -217,7 +217,7 @@ extern struct kobject *firmware_kobj;
>  
>  int kobject_uevent(struct kobject *kobj, enum kobject_action action);
>  int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
> -			char *envp[]);
> +			const char * const envp[]);
>  int kobject_synth_uevent(struct kobject *kobj, const char *buf, size_t count);
>  
>  __printf(2, 3)
> diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> index 63d0816ab23b..9107989a0cc8 100644
> --- a/lib/kobject_uevent.c
> +++ b/lib/kobject_uevent.c
> @@ -452,7 +452,7 @@ static void zap_modalias_env(struct kobj_uevent_env *env)
>   * corresponding error when it fails.
>   */
>  int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
> -		       char *envp_ext[])
> +		       const char * const envp_ext[])
>  {
>  	struct kobj_uevent_env *env;
>  	const char *action_string = kobject_actions[action];

No objection from me, care to make it a real patch so that I can apply
it after 4.18-rc1 is out?

thanks,

greg k-h