From: Matan Peled <chaosite@gmail.com>
To: Andrew Morton <akpm@osdl.org>
Cc: David Singleton <daviado@gmail.com>,
mingo@elte.hu, linux-kernel@vger.kernel.org, drepper@gmail.com,
robustmutexes@lists.osdl.org
Subject: Re: Robust futex patch for Linux 2.6.15
Date: Sat, 14 Jan 2006 18:13:46 +0200 [thread overview]
Message-ID: <43C9233A.20504@gmail.com> (raw)
In-Reply-To: <20060113132704.207336d7.akpm@osdl.org>
Andrew Morton wrote:
> Please send the patch to this mailing list with a full description, as per
> http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt. And by "full" I
> mean something which tells us what a "robust futex" actually is (it's been
> a year since I thought about them) and why we would want such a thing.
>
> This code looks racy:
>
> +static int futex_deadlock(struct rt_mutex *lock)
> +{
> + DEFINE_WAIT(wait);
> +
> + _raw_spin_unlock(&lock->wait_lock);
> + _raw_spin_unlock(¤t->pi_lock);
> +
> + prepare_to_wait(&deadlocked_futex, &wait, TASK_INTERRUPTIBLE);
> + schedule();
> + finish_wait(&deadlocked_futex, &wait);
> +
> + return -EDEADLK;
> +}
>
> If the spin_unlocks happened after the prepare_to_wait then it would be
> more idoimatic, but without having analysed the wakeup path, I wonder if a
> wakeup which occurs after the spin_unlocks and before the prepare_to_wait()
> will get lost.
Andrew, I'm looking at this:
http://source.mvista.com/~dsingleton/robust-futex-1
And it doesn't seem to have a futex_deadlock function at all. In fact, its seems
to have a rather lengthy description about robust futexes and why they're a Good
Thing(TM).
What are you looking at?
--
[Name ] :: [Matan I. Peled ]
[Location ] :: [Israel ]
[Public Key] :: [0xD6F42CA5 ]
[Keyserver ] :: [keyserver.kjsl.com]
encrypted/signed plain text preferred
next prev parent reply other threads:[~2006-01-14 16:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <b324b5ad0601131316m721f959eu37b741f9e5557a2e@mail.gmail.com>
2006-01-13 21:27 ` Robust futex patch for Linux 2.6.15 Andrew Morton
2006-01-13 22:20 ` Andi Kleen
2006-01-13 23:01 ` Andrew Morton
2006-01-14 16:13 ` Matan Peled [this message]
2006-01-14 20:25 ` Andrew Morton
2006-01-16 19:09 ` Re [robust-futex-2] : interdiff for memory leak fix david singleton
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=43C9233A.20504@gmail.com \
--to=chaosite@gmail.com \
--cc=akpm@osdl.org \
--cc=daviado@gmail.com \
--cc=drepper@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=robustmutexes@lists.osdl.org \
/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).