From: Michal Hocko <mhocko@kernel.org>
To: "Michal Koutný" <mkoutny@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mateusz Guzik <mguzik@redhat.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Vlastimil Babka <vbabka@suse.cz>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Arun KS <arunks@codeaurora.org>,
Bartosz Golaszewski <brgl@bgdev.pl>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: get_cmdline use arg_lock instead of mmap_sem
Date: Wed, 17 Apr 2019 15:41:52 +0200 [thread overview]
Message-ID: <20190417134152.GM5878@dhcp22.suse.cz> (raw)
In-Reply-To: <20190417120347.15397-1-mkoutny@suse.com>
On Wed 17-04-19 14:03:47, Michal Koutny wrote:
> The commit a3b609ef9f8b ("proc read mm's {arg,env}_{start,end} with mmap
> semaphore taken.") added synchronization of reading argument/environment
> boundaries under mmap_sem. Later commit 88aa7cc688d4 ("mm: introduce
> arg_lock to protect arg_start|end and env_start|end in mm_struct")
> avoided the coarse use of mmap_sem in similar situations.
>
> get_cmdline can also use arg_lock instead of mmap_sem when it reads the
> boundaries.
Don't we need to use the lock in prctl_set_mm as well then?
> Signed-off-by: Michal Koutný <mkoutny@suse.com>
> ---
> mm/util.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/util.c b/mm/util.c
> index d559bde497a9..568575cceefc 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -758,12 +758,12 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
> if (!mm->arg_end)
> goto out_mm; /* Shh! No looking before we're done */
>
> - down_read(&mm->mmap_sem);
> + spin_lock(&mm->arg_lock);
> arg_start = mm->arg_start;
> arg_end = mm->arg_end;
> env_start = mm->env_start;
> env_end = mm->env_end;
> - up_read(&mm->mmap_sem);
> + spin_unlock(&mm->arg_lock);
>
> len = arg_end - arg_start;
>
> --
> 2.16.4
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-04-17 13:41 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-17 12:03 [PATCH] mm: get_cmdline use arg_lock instead of mmap_sem Michal Koutný
2019-04-17 13:41 ` Michal Hocko [this message]
2019-04-17 14:41 ` Michal Koutný
2019-04-17 14:55 ` Michal Hocko
2019-04-18 13:50 ` [PATCH] prctl_set_mm: downgrade mmap_sem to read lock Michal Koutný
2019-04-18 14:09 ` Cyrill Gorcunov
2019-04-18 14:15 ` Michal Hocko
2019-04-18 14:27 ` Laurent Dufour
2019-04-18 18:23 ` Cyrill Gorcunov
2019-04-30 8:18 ` [PATCH 0/3] Reduce mmap_sem usage for args manipulation Michal Koutný
2019-04-30 8:18 ` [PATCH 1/3] mm: get_cmdline use arg_lock instead of mmap_sem Michal Koutný
2019-04-30 9:09 ` Kirill Tkhai
2019-04-30 9:38 ` Cyrill Gorcunov
2019-04-30 9:53 ` Kirill Tkhai
2019-04-30 10:45 ` Cyrill Gorcunov
2019-04-30 10:56 ` Michal Koutný
2019-04-30 13:24 ` Cyrill Gorcunov
2019-04-30 8:18 ` [PATCH 2/3] prctl_set_mm: Refactor checks from validate_prctl_map Michal Koutný
2019-04-30 9:27 ` Kirill Tkhai
2019-04-30 8:18 ` [PATCH 3/3] prctl_set_mm: downgrade mmap_sem to read lock Michal Koutný
2019-04-30 8:55 ` Kirill Tkhai
2019-04-30 9:08 ` Cyrill Gorcunov
2019-04-30 9:11 ` Kirill Tkhai
2019-05-02 12:52 ` [PATCH v3 0/2] Reduce mmap_sem usage for args manipulation Michal Koutný
2019-05-02 12:52 ` [PATCH v3 1/2] prctl_set_mm: Refactor checks from validate_prctl_map Michal Koutný
2019-05-02 20:57 ` Cyrill Gorcunov
2019-05-02 12:52 ` [PATCH v3 2/2] prctl_set_mm: downgrade mmap_sem to read lock Michal Koutný
2019-05-02 20:57 ` Cyrill Gorcunov
2019-05-06 9:28 ` Kirill Tkhai
2019-05-07 17:42 ` Michal Hocko
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=20190417134152.GM5878@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=arunks@codeaurora.org \
--cc=brgl@bgdev.pl \
--cc=geert+renesas@glider.be \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mguzik@redhat.com \
--cc=mkoutny@suse.com \
--cc=rppt@linux.ibm.com \
--cc=vbabka@suse.cz \
/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).