linux-kernel - Re: [PATCH v4 1/5] mm: Provide kernel parameter to allow disabling page init poisoning

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Message-ID: <3c045f79-c18b-47dd-4017-a024edc9aa46@microsoft.com>
Date:   Fri, 21 Sep 2018 19:52:42 +0000
From:   Pasha Tatashin <Pavel.Tatashin@...rosoft.com>
To:     Logan Gunthorpe <logang@...tatee.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
CC:     "mhocko@...e.com" <mhocko@...e.com>,
        "dave.jiang@...el.com" <dave.jiang@...el.com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "dave.hansen@...el.com" <dave.hansen@...el.com>,
        "jglisse@...hat.com" <jglisse@...hat.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v4 1/5] mm: Provide kernel parameter to allow disabling
 page init poisoning



On 9/21/18 3:41 PM, Logan Gunthorpe wrote:
> On 2018-09-21 1:04 PM, Pasha Tatashin wrote:
>>
>>> +			pr_err("vm_debug option '%c' unknown. skipped\n",
>>> +			       *str);
>>> +		}
>>> +
>>> +		str++;
>>> +	}
>>> +out:
>>> +	if (page_init_poisoning && !__page_init_poisoning)
>>> +		pr_warn("Page struct poisoning disabled by kernel command line option 'vm_debug'\n");
>>
>> New lines '\n' can be removed, they are not needed for kprintfs.
> 
> No, that's not correct.
> 
> A printk without a newline termination is not emitted
> as output until the next printk call. (To support KERN_CONT).
> Therefore removing the '\n' causes a printk to not be printed when it is
> called which can cause long delayed messages and subtle problems when
> debugging. Always keep the newline in place even though the kernel will
> add one for you if it's missing.

OK. Thank you for clarifying Logan. I've seen new lines are being
removed in other patches,

Pavel