From: John David Anglin <dave.anglin@bell.net>
To: Helge Deller <deller@gmx.de>,
linux-parisc@vger.kernel.org,
James Bottomley <James.Bottomley@hansenpartnership.com>
Subject: Re: [PATCH][RFC] parisc: Use ldcw,co on uniprocessor machines only
Date: Wed, 11 Dec 2019 16:29:06 -0500 [thread overview]
Message-ID: <63f37f01-6ae1-96e2-815b-aa48eb1f1c31@bell.net> (raw)
In-Reply-To: <20191211201634.GA13407@ls3530.fritz.box>
On 2019-12-11 3:16 p.m., Helge Deller wrote:
> Up to now we tried to optimize the ldcw usage by using the coherent
> completer of this command, which operates on the cache (instead of
> memory) and thus might speed up things, and which was enabled by default
> on our 64bit kernel build.
>
> But we still see runtime locking problems, so this patch changes it back
> to use ldcw for 32- and 64-bit kernels, and live-patches it at runtime
> to use the coherent completer when running on a uniprocessor machine.
I'm not convinced this is the problem. Nominally, every PA 2.0 machine that we support is coherent.
Is there evidence that this actually helps? I did a test where I switched "ldcw,co" to "ldcw" and
didn't find a significant difference. So, I left the default assumption that most PA 2.0 machines
are coherent in gcc.
I'm seeing different behavior for pthread_mutex_lock/pthread_mutex_unlock with different
glibc versions. The locking issues also seem to vary from one kernel version to the next.
I don't know that we can blame the two build failures of acl2_8.1dfsg-6 on phantom on a
locking issue, but phantom failed twice at the same pwasoint. In both cases, cc1 terminated with
a segmentation fault. Yet, mx3210 has been chugging away for more than a day on the package.
It also built -4 and -5.
I don't have a clue what's really wrong but I suspect the slowness of our locking infrastructure
is what exposes these issues.
I've seen one issue in user space where a pointer to a mutex got corrupted in apt-cacher-ng.
If I remember correctly, the LWS locking code was spinning with a pointer value of 0x12. I think
the code should have faulted but the thread stuck. Had to systemctl restart apt-cacher-ng.
Dave
--
John David Anglin dave.anglin@bell.net
next prev parent reply other threads:[~2019-12-11 21:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-11 20:16 [PATCH][RFC] parisc: Use ldcw,co on uniprocessor machines only Helge Deller
2019-12-11 21:29 ` John David Anglin [this message]
2019-12-12 9:01 ` Helge Deller
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=63f37f01-6ae1-96e2-815b-aa48eb1f1c31@bell.net \
--to=dave.anglin@bell.net \
--cc=James.Bottomley@hansenpartnership.com \
--cc=deller@gmx.de \
--cc=linux-parisc@vger.kernel.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).