From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
Balbir Singh <bsingharora@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Nicholas Piggin <nicholas.piggin@gmail.com>
Subject: Re: [RFC][PATCH] Fix a race between rwsem and the scheduler
Date: Thu, 01 Sep 2016 07:47:10 +1000 [thread overview]
Message-ID: <1472680030.2388.95.camel@kernel.crashing.org> (raw)
In-Reply-To: <20160831133104.GD10153@twins.programming.kicks-ass.net>
On Wed, 2016-08-31 at 15:31 +0200, Peter Zijlstra wrote:
> On Wed, Aug 31, 2016 at 07:28:18AM +1000, Benjamin Herrenschmidt
> wrote:
>
> >
> > On powerpc we have a sync deep in _switch to achieve that.
>
> OK, for giggles, could you (or Balbir) check what happens if you take
> that sync out?
>
> There should be enough serialization in the generic code to cover the
> case that code mentions.
>
> ARM64 has a stronger barrier in its context switch code, but that's
> because they need to sync against external agents (like their TLB and
> cache) and no amount of generic locking is going to cover that.
The problem is no amount of testing can tell you it works for sure :-)
I would be nervous not having a real full sync in _switch. All we have
along the scheduler path is lwsync's and our isync based load construct
for spin_lock, I'm not sure what other assumptions we have around that
sync in there...
Cheers,
Ben.
next prev parent reply other threads:[~2016-08-31 21:47 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-30 8:49 Balbir Singh
2016-08-30 9:13 ` Nicholas Piggin
2016-08-30 12:19 ` Peter Zijlstra
2016-08-30 13:04 ` Oleg Nesterov
2016-08-30 14:13 ` Peter Zijlstra
2016-08-30 16:57 ` Oleg Nesterov
2016-08-30 18:34 ` Peter Zijlstra
2016-08-30 21:28 ` Benjamin Herrenschmidt
2016-08-31 7:18 ` Peter Zijlstra
2016-08-31 10:56 ` Benjamin Herrenschmidt
2016-08-31 13:31 ` Peter Zijlstra
2016-08-31 21:47 ` Benjamin Herrenschmidt [this message]
2016-09-01 6:49 ` Balbir Singh
2016-09-01 6:57 ` Peter Zijlstra
2016-09-01 14:17 ` Boqun Feng
2016-09-01 15:33 ` Peter Zijlstra
2016-08-30 21:25 ` Benjamin Herrenschmidt
2016-08-31 7:20 ` Peter Zijlstra
2016-08-31 10:55 ` Benjamin Herrenschmidt
2016-08-31 3:41 ` Balbir Singh
2016-08-31 7:28 ` Peter Zijlstra
2016-08-31 10:17 ` Balbir Singh
2016-08-31 10:57 ` Benjamin Herrenschmidt
2016-09-01 1:48 ` Alexey Kardashevskiy
2016-09-01 12:16 ` Alexey Kardashevskiy
2016-08-30 12:58 ` Oleg Nesterov
2016-08-31 3:25 ` Balbir Singh
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=1472680030.2388.95.camel@kernel.crashing.org \
--to=benh@kernel.crashing.org \
--cc=bsingharora@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=nicholas.piggin@gmail.com \
--cc=oleg@redhat.com \
--cc=peterz@infradead.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
Powered by JetHome