linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Matthew Wilcox <willy@infradead.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: akpm@linux-foundation.org, Mike Kravetz <mike.kravetz@oracle.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] mm/hugetlb: make hugetlb_lock irq safe
Date: Wed, 5 Sep 2018 06:04:40 -0700	[thread overview]
Message-ID: <20180905130440.GA3729@bombadil.infradead.org> (raw)
In-Reply-To: <20180905112341.21355-1-aneesh.kumar@linux.ibm.com>

On Wed, Sep 05, 2018 at 04:53:41PM +0530, Aneesh Kumar K.V wrote:
>  inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.

How do you go from "can be taken in softirq context" problem report to
"must disable hard interrupts" solution?  Please explain why spin_lock_bh()
is not a sufficient fix.

>  swapper/68/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
>  0000000052a030a7 (hugetlb_lock){+.?.}, at: free_huge_page+0x9c/0x340
>  {SOFTIRQ-ON-W} state was registered at:
>    lock_acquire+0xd4/0x230
>    _raw_spin_lock+0x44/0x70
>    set_max_huge_pages+0x4c/0x360
>    hugetlb_sysctl_handler_common+0x108/0x160
>    proc_sys_call_handler+0x134/0x190
>    __vfs_write+0x3c/0x1f0
>    vfs_write+0xd8/0x220

Also, this only seems to trigger here.  Is it possible we _already_
have softirqs disabled through every other code path, and it's just this
one sysctl handler that needs to disable softirqs?  Rather than every
lock access?

I'm not seeing any analysis in this patch description, just a kneejerk
"lockdep complained, must disable interrupts".


  reply	other threads:[~2018-09-05 13:04 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-05 11:23 [RFC PATCH] mm/hugetlb: make hugetlb_lock irq safe Aneesh Kumar K.V
2018-09-05 13:04 ` Matthew Wilcox [this message]
2018-09-05 13:26   ` Aneesh Kumar K.V
2018-09-05 13:48     ` Matthew Wilcox
2018-09-05 19:58       ` Andrew Morton
2018-09-05 21:35         ` Mike Kravetz
2018-09-05 22:00           ` Andrew Morton
2018-09-05 23:07             ` Matthew Wilcox
2018-09-05 23:51               ` Mike Kravetz
2018-09-06  4:03                 ` Aneesh Kumar K.V
2018-09-06 11:19                 ` Michal Hocko
2018-09-06  3:58           ` Aneesh Kumar K.V
2018-09-06  3:54         ` Aneesh Kumar K.V
2018-09-06  4:00       ` Aneesh Kumar K.V

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180905130440.GA3729@bombadil.infradead.org \
    --to=willy@infradead.org \
    --cc=akpm@linux-foundation.org \
    --cc=aneesh.kumar@linux.ibm.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mike.kravetz@oracle.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).