archive mirror
 help / color / mirror / Atom feed
From: "Aneesh Kumar K.V" <>
To: Matthew Wilcox <>
Cc:, Mike Kravetz <>,,
Subject: Re: [RFC PATCH] mm/hugetlb: make hugetlb_lock irq safe
Date: Wed, 5 Sep 2018 18:56:19 +0530	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 09/05/2018 06:34 PM, Matthew Wilcox wrote:
> 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?

Are you asking whether I looked at moving that put_page to a worker 
thread? I didn't. The reason I looked at current patch is to enable the 
usage of put_page() from irq context. We do allow that for non hugetlb 
pages. So was not sure adding that additional restriction for hugetlb
is really needed. Further the conversion to irqsave/irqrestore was

Now with respect to making sure we don't have irq already disabled in 
those code paths, I did check that. But let me know if you find anything 
I missed.

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


  reply	other threads:[~2018-09-05 13:26 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
2018-09-05 13:26   ` Aneesh Kumar K.V [this message]
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:

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

  git send-email \ \ \ \ \ \ \ \

* 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).