From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Petr Mladek <pmladek@suse.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] printk: Remove superfluous memory barriers from printk_safe
Date: Mon, 16 Oct 2017 20:05:30 +0900 [thread overview]
Message-ID: <20171016110530.GA6316@tigerII.localdomain> (raw)
In-Reply-To: <20171015202715.5c3bb075@vmware.local.home>
On (10/15/17 20:27), Steven Rostedt wrote:
> > On (10/11/17 12:46), Steven Rostedt wrote:
> > > From: Steven Rostedt (VMware) <rostedt@goodmis.org>
> > >
> > > The variable printk_safe_irq_ready is set and never cleared at system
> > > boot up, when there's only one CPU active. It is set before other
> > > CPUs come on line. Also, it is extremely unlikely that an NMI would
> > > trigger this early in boot up (which I wonder why we even have this
> > > variable at all).
> >
> > it's not only NMI related, printk() recursion can happen at any stages,
> > including... um... wait a second. ... including the "before we set up
> > per-CPU areas" stage? hmm... smells like a bug?
>
> I think this was just being overly paranoid.
hm, printk recursion is pretty easy to trigger. vscnprintf() can WARN_ON(),
for instance. just pass (mistakenly) unknown printk specifier, e.g.
%A, and this will do.
-ss
prev parent reply other threads:[~2017-10-16 11:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-11 16:46 [PATCH] printk: Remove superfluous memory barriers from printk_safe Steven Rostedt
2017-10-12 9:34 ` Petr Mladek
2017-10-14 9:21 ` Sergey Senozhatsky
2017-10-16 0:27 ` Steven Rostedt
2017-10-16 8:12 ` Petr Mladek
2017-10-16 11:08 ` Sergey Senozhatsky
2017-10-16 11:05 ` Sergey Senozhatsky [this message]
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=20171016110530.GA6316@tigerII.localdomain \
--to=sergey.senozhatsky@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.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).