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From: Luis Chamberlain <mcgrof@kernel.org>
To: Xiaoming Ni <nixiaoming@huawei.com>
Cc: keescook@chromium.org, yzaikin@google.com, adobriyan@gmail.com,
	mingo@kernel.org, gpiccoli@canonical.com, rdna@fb.com,
	patrick.bellasi@arm.com, sfr@canb.auug.org.au,
	akpm@linux-foundation.org, mhocko@suse.com,
	penguin-kernel@i-love.sakura.ne.jp, vbabka@suse.cz,
	tglx@linutronix.de, peterz@infradead.org,
	Jisheng.Zhang@synaptics.com, khlebnikov@yandex-team.ru,
	bigeasy@linutronix.de, pmladek@suse.com,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	wangle6@huawei.com, alex.huangjianhui@huawei.com
Subject: Re: [PATCH v4 1/4] sysctl: Add register_sysctl_init() interface
Date: Fri, 29 May 2020 11:31:24 +0000	[thread overview]
Message-ID: <20200529113124.GZ11244@42.do-not-panic.com> (raw)
In-Reply-To: <abdab2be-91e2-5f9b-bf49-abc387072a31@huawei.com>

On Fri, May 29, 2020 at 04:33:01PM +0800, Xiaoming Ni wrote:
> On 2020/5/29 15:36, Luis Chamberlain wrote:
> > On Fri, May 29, 2020 at 03:27:22PM +0800, Xiaoming Ni wrote:
> > > On 2020/5/29 15:09, Luis Chamberlain wrote:
> > > > On Tue, May 19, 2020 at 11:31:08AM +0800, Xiaoming Ni wrote:
> > > > > --- a/kernel/sysctl.c
> > > > > +++ b/kernel/sysctl.c
> > > > > @@ -3358,6 +3358,25 @@ int __init sysctl_init(void)
> > > > >    	kmemleak_not_leak(hdr);
> > > > >    	return 0;
> > > > >    }
> > > > > +
> > > > > +/*
> > > > > + * The sysctl interface is used to modify the interface value,
> > > > > + * but the feature interface has default values. Even if register_sysctl fails,
> > > > > + * the feature body function can also run. At the same time, malloc small
> > > > > + * fragment of memory during the system initialization phase, almost does
> > > > > + * not fail. Therefore, the function return is designed as void
> > > > > + */
> > > > 
> > > > Let's use kdoc while at it. Can you convert this to proper kdoc?
> > > > 
> > > Sorry, I do n’t know the format requirements of Kdoc, can you give me some
> > > tips for writing?
> > 
> > Sure, include/net/mac80211.h is a good example.
> > 
> > > > > +void __init register_sysctl_init(const char *path, struct ctl_table *table,
> > > > > +				 const char *table_name)
> > > > > +{
> > > > > +	struct ctl_table_header *hdr = register_sysctl(path, table);
> > > > > +
> > > > > +	if (unlikely(!hdr)) {
> > > > > +		pr_err("failed when register_sysctl %s to %s\n", table_name, path);
> > > > > +		return;
> > > > 
> > > > table_name is only used for this, however we can easily just make
> > > > another _register_sysctl_init() helper first, and then use a macro
> > > > which will concatenate this to something useful if you want to print
> > > > a string. I see no point in the description for this, specially since
> > > > the way it was used was not to be descriptive, but instead just a name
> > > > followed by some underscore and something else.
> > > > 
> > > Good idea, I will fix and send the patch to you as soon as possible
> > 
> > No rush :)
> > 
> > > > > +	}
> > > > > +	kmemleak_not_leak(hdr);
> > > > 
> > > > Is it *wrong* to run kmemleak_not_leak() when hdr was not allocated?
> > > > If so, can you fix the sysctl __init call itself?
> > > I don't understand here, do you mean that register_sysctl_init () does not
> > > need to call kmemleak_not_leak (hdr), or does it mean to add check hdr
> > > before calling kmemleak_not_leak (hdr) in sysctl_init ()?
> > 
> > I'm asking that the way you are adding it, you don't run
> > kmemleak_not_leak(hdr) if the hdr allocation filed. If that is
> > right then it seems that sysctl_init() might not be doing it
> > right.
> > 
> > Can that code be shared somehow?
> > 
> >    Luis
> 
> void __ref kmemleak_not_leak(const void *ptr)
> {
> 	pr_debug("%s(0x%p)\n", __func__, ptr);
> 
> 	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
> 		make_gray_object((unsigned long)ptr);
> }
> EXPORT_SYMBOL(kmemleak_not_leak);
> 
> In the code of kmemleak_not_leak(), it is verified that the pointer is
> valid, so kmemleak_not_leak (NULL) will not be a problem.
> At the same time, there is no need to call kmemleak_not_leak() in the failed
> branch of register_sysctl_init().

Thanks for the confirmation.

   Luis

  reply	other threads:[~2020-05-29 11:31 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19  3:31 [PATCH v4 0/4] cleaning up the sysctls table (hung_task watchdog) Xiaoming Ni
2020-05-19  3:31 ` [PATCH v4 1/4] sysctl: Add register_sysctl_init() interface Xiaoming Ni
2020-05-29  7:09   ` Luis Chamberlain
2020-05-29  7:27     ` Xiaoming Ni
2020-05-29  7:36       ` Luis Chamberlain
2020-05-29  8:33         ` Xiaoming Ni
2020-05-29 11:31           ` Luis Chamberlain [this message]
2020-05-19  3:31 ` [PATCH v4 2/4] sysctl: Move some boundary constants form sysctl.c to sysctl_vals Xiaoming Ni
2020-05-19  4:44   ` Tetsuo Handa
2020-05-20  1:14     ` Xiaoming Ni
2020-05-20  1:39       ` Luis Chamberlain
2020-05-19  3:31 ` [PATCH v4 3/4] hung_task: Move hung_task sysctl interface to hung_task.c Xiaoming Ni
2020-05-19  3:31 ` [PATCH v4 4/4] watchdog: move watchdog sysctl interface to watchdog.c Xiaoming Ni
2020-05-20  3:31 ` [PATCH v4 0/4] cleaning up the sysctls table (hung_task watchdog) Andrew Morton
2020-05-20  4:02   ` Xiaoming Ni
2020-05-20 13:08     ` Luis Chamberlain

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