LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Mark Rutland <mark.rutland@arm.com>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Marco Elver <elver@google.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Anders Roxell <anders.roxell@linaro.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexander Potapenko <glider@google.com>,
	Dmitry Vyukov <dvyukov@google.com>, Jann Horn <jannh@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	kasan-dev <kasan-dev@googlegroups.com>,
	rcu@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Tejun Heo <tj@kernel.org>, Lai Jiangshan <jiangshanlai@gmail.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: linux-next: stall warnings and deadlock on Arm64 (was: [PATCH] kfence: Avoid stalling...)
Date: Fri, 20 Nov 2020 15:22:00 +0000
Message-ID: <20201120152200.GD2328@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20201120143928.GH1437@paulmck-ThinkPad-P72>

On Fri, Nov 20, 2020 at 06:39:28AM -0800, Paul E. McKenney wrote:
> On Fri, Nov 20, 2020 at 03:19:28PM +0100, Marco Elver wrote:
> > I found that disabling ftrace for some of kernel/rcu (see below) solved
> > the stalls (and any mention of deadlocks as a side-effect I assume),
> > resulting in successful boot.
> > 
> > Does that provide any additional clues? I tried to narrow it down to 1-2
> > files, but that doesn't seem to work.
> 
> There were similar issues during the x86/entry work.  Are the ARM guys
> doing arm64/entry work now?

I'm currently looking at it. I had been trying to shift things to C for
a while, and right now I'm trying to fix the lockdep state tracking,
which is requiring untangling lockdep/rcu/tracing.

The main issue I see remaining atm is that we don't save/restore the
lockdep state over exceptions taken from kernel to kernel. That could
result in lockdep thinking IRQs are disabled when they're actually
enabled (because code in the nested context might do a save/restore
while IRQs are disabled, then return to a context where IRQs are
enabled), but AFAICT shouldn't result in the inverse in most cases since
the non-NMI handlers all call lockdep_hardirqs_disabled().

I'm at a loss to explaim the rcu vs ftrace bits, so if you have any
pointers to the issuies ween with the x86 rework that'd be quite handy.

Thanks,
Mark.

> 
> 							Thanx, Paul
> 
> > Thanks,
> > -- Marco
> > 
> > ------ >8 ------
> > 
> > diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
> > index 0cfb009a99b9..678b4b094f94 100644
> > --- a/kernel/rcu/Makefile
> > +++ b/kernel/rcu/Makefile
> > @@ -3,6 +3,13 @@
> >  # and is generally not a function of system call inputs.
> >  KCOV_INSTRUMENT := n
> >  
> > +ifdef CONFIG_FUNCTION_TRACER
> > +CFLAGS_REMOVE_update.o = $(CC_FLAGS_FTRACE)
> > +CFLAGS_REMOVE_sync.o = $(CC_FLAGS_FTRACE)
> > +CFLAGS_REMOVE_srcutree.o = $(CC_FLAGS_FTRACE)
> > +CFLAGS_REMOVE_tree.o = $(CC_FLAGS_FTRACE)
> > +endif
> > +
> >  ifeq ($(CONFIG_KCSAN),y)
> >  KBUILD_CFLAGS += -g -fno-omit-frame-pointer
> >  endif

  reply index

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-10 13:53 [PATCH] kfence: Avoid stalling work queue task without allocations Marco Elver
2020-11-10 14:25 ` Dmitry Vyukov
2020-11-10 14:53   ` Marco Elver
2020-11-10 23:23 ` Anders Roxell
2020-11-11  8:29   ` Marco Elver
2020-11-11 13:38     ` Marco Elver
2020-11-11 18:05       ` Steven Rostedt
2020-11-11 18:23         ` Paul E. McKenney
2020-11-11 18:34           ` Marco Elver
2020-11-11 19:21             ` Paul E. McKenney
2020-11-11 20:21               ` Marco Elver
2020-11-12  0:11                 ` Paul E. McKenney
2020-11-12 12:49                   ` Marco Elver
2020-11-12 16:14                     ` Marco Elver
2020-11-12 17:54                       ` Paul E. McKenney
2020-11-12 18:12                         ` Marco Elver
2020-11-12 20:00                           ` Paul E. McKenney
2020-11-13 11:06                             ` Marco Elver
2020-11-13 17:20                               ` Paul E. McKenney
2020-11-13 17:57                         ` Paul E. McKenney
2020-11-17 10:52                           ` Marco Elver
2020-11-17 18:29                             ` Paul E. McKenney
2020-11-18 22:56                               ` Marco Elver
2020-11-18 23:38                                 ` Paul E. McKenney
2020-11-19 12:53                                   ` Marco Elver
2020-11-19 15:14                                     ` Paul E. McKenney
2020-11-19 17:02                                       ` Marco Elver
2020-11-19 18:48                                         ` Paul E. McKenney
2020-11-19 19:38                                           ` linux-next: stall warnings and deadlock on Arm64 (was: [PATCH] kfence: Avoid stalling...) Marco Elver
2020-11-19 21:35                                             ` Paul E. McKenney
2020-11-19 22:53                                               ` Will Deacon
2020-11-20 10:30                                                 ` Mark Rutland
2020-11-20 14:03                                                   ` Marco Elver
2020-11-23 19:32                                                     ` Mark Rutland
2020-11-24 14:03                                                       ` Marco Elver
2020-11-24 15:01                                                         ` Paul E. McKenney
2020-11-24 19:43                                                           ` Mark Rutland
2020-11-24 20:32                                                             ` Steven Rostedt
2020-11-24 19:30                                                         ` Mark Rutland
2020-11-25  9:45                                                           ` Marco Elver
2020-11-25 10:28                                                             ` Mark Rutland
2020-11-20 14:19                                               ` Marco Elver
2020-11-20 14:39                                                 ` Paul E. McKenney
2020-11-20 15:22                                                   ` Mark Rutland [this message]
2020-11-20 17:38                                                     ` Paul E. McKenney
2020-11-20 18:02                                                       ` Mark Rutland
2020-11-20 18:57                                                         ` Paul E. McKenney
2020-11-20 15:26                                                 ` Steven Rostedt
2020-11-20 18:17                                                   ` Marco Elver
2020-11-20 18:57                                                     ` Steven Rostedt
2020-11-20 19:16                                                     ` Steven Rostedt
2020-11-20 19:22                                                       ` Marco Elver
2020-11-20 19:27                                     ` [PATCH] kfence: Avoid stalling work queue task without allocations Steven Rostedt
2020-11-23 15:27                                       ` Marco Elver
2020-11-23 16:28                                         ` Steven Rostedt
2020-11-23 16:36                                           ` Steven Rostedt
2020-11-23 18:53                                             ` Marco Elver
2020-11-23 18:42                                           ` Steven Rostedt
2020-11-24  2:59                                             ` Boqun Feng
2020-11-24  3:44                                               ` Paul E. McKenney
2020-11-11 18:21       ` Paul E. McKenney
2020-11-11 15:01     ` Anders Roxell
2020-11-11 15:22       ` Marco Elver

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=20201120152200.GD2328@C02TD0UTHF1T.local \
    --to=mark.rutland@arm.com \
    --cc=akpm@linux-foundation.org \
    --cc=anders.roxell@linaro.org \
    --cc=dvyukov@google.com \
    --cc=elver@google.com \
    --cc=glider@google.com \
    --cc=jannh@google.com \
    --cc=jiangshanlai@gmail.com \
    --cc=kasan-dev@googlegroups.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=paulmck@kernel.org \
    --cc=peterz@infradead.org \
    --cc=rcu@vger.kernel.org \
    --cc=rostedt@goodmis.org \
    --cc=tj@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

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git
	git clone --mirror https://lore.kernel.org/lkml/10 lkml/git/10.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git