From: Sebastian Huber <sebastian.huber@embedded-brains.de>
To: Volodymyr Medvid <vmedvid@riseup.net>, newlib@sourceware.org
Subject: Re: [PATCH] Fix stdio memory leaks with _REENT_SMALL + _LITE_EXIT
Date: Tue, 12 Apr 2022 18:10:38 +0200 [thread overview]
Message-ID: <795ccb59-38d3-a9d8-f8d4-9314689d1c62@embedded-brains.de> (raw)
In-Reply-To: <20220412132313.39160-1-vmedvid@riseup.net>
On 12/04/2022 15:23, Volodymyr Medvid wrote:
> When a thread calls stdio functions (say, printf) and then dies,
> _reclaim_reent() runs cleanup_stdio() to free the file buffers
> and descriptors created for this thread. This is causing multiple
> memory leaks when newlib is configured with _REENT_SMALL
> and _LITE_EXIT - this is the standard configuration for
> newlib-nano provided with GNU Arm Embedded Toolchain.
>
> 1. While __sfp() allocates the FILE objects in GLOBAL_REENT glue chain,
> stdio_cleanup walks through the thread-specific glue chain
> to run the cleanup_func. Therefore, the FILE objects are never
> freed. This leaks ~428 bytes per thread (glue_with_file + 3 x FILE).
Yes, this is the Newlib design. FILE objects are never freed. If you
close a FILE object, then it is basically placed on a free list and
recycled once another FILE object is opened.
>
> To fix this, update __sfp() to use the per-thread glue chain for
> stdio descriptors.
This is definitely not the right way to address this issue.
Why don't you use the _REENT_GLOBAL_STDIO_STREAMS Newlib configuration
option?
>
> 2. With _LITE_EXIT enabled, _fflush_r is used as cleanup_func
> instead of _fclose_r - as a result, the I/O buffer memory allocated
> by __smakebuf_r is never freed - this leaks another 1024 bytes.
> To fix this, update cleanup_stdio to always use _fclose_r.
>
> This is a follow-up patch forhttps://ecos.sourceware.org/ml/newlib/current/017697.html
> ---
> newlib/libc/stdio/findfp.c | 9 ++-------
> 1 file changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/newlib/libc/stdio/findfp.c b/newlib/libc/stdio/findfp.c
> index 1370b63b8..2799980f3 100644
> --- a/newlib/libc/stdio/findfp.c
> +++ b/newlib/libc/stdio/findfp.c
> @@ -153,7 +153,7 @@ __sfp (struct _reent *d)
>
> if (_GLOBAL_REENT->__cleanup == NULL)
> __sinit (_GLOBAL_REENT);
> - for (g = &_GLOBAL_REENT->__sglue;; g = g->_next)
> + for (g = &d->__sglue;; g = g->_next)
> {
> for (fp = g->_iobs, n = g->_niobs; --n >= 0; fp++)
> if (fp->_flags == 0)
This patch would break at least RTEMS.
--
embedded brains GmbH
Herr Sebastian HUBER
Dornierstr. 4
82178 Puchheim
Germany
email: sebastian.huber@embedded-brains.de
phone: +49-89-18 94 741 - 16
fax: +49-89-18 94 741 - 08
Registergericht: Amtsgericht München
Registernummer: HRB 157899
Vertretungsberechtigte Geschäftsführer: Peter Rasmussen, Thomas Dörfler
Unsere Datenschutzerklärung finden Sie hier:
https://embedded-brains.de/datenschutzerklaerung/
next prev parent reply other threads:[~2022-04-12 16:10 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-12 13:23 Volodymyr Medvid
2022-04-12 16:10 ` Sebastian Huber [this message]
2022-04-12 20:57 ` Volodymyr Medvid
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=795ccb59-38d3-a9d8-f8d4-9314689d1c62@embedded-brains.de \
--to=sebastian.huber@embedded-brains.de \
--cc=newlib@sourceware.org \
--cc=vmedvid@riseup.net \
/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 read-only IMAP folder(s) and NNTP newsgroup(s).