From: Olaf Hering <olaf@aepfle.de>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: acquire_console_mutex: WARNING: at 2.6.33.4-rt20/kernel/mutex-debug.c:65 mutex_remove_waiter+0xe8/0x11c()
Date: Sun, 30 May 2010 23:39:02 +0200 [thread overview]
Message-ID: <20100530213902.GA3619@aepfle.de> (raw)
In-Reply-To: <201005251318.37242.arnd@arndb.de>
On Tue, May 25, Arnd Bergmann wrote:
> On Tuesday 25 May 2010, Olaf Hering wrote:
> > I get this warning when busybox /sbin/init opens the console.
> > It does not happen when CONFIG_PREEMPT_RT is enabled.
> > Any ideas how to fix it for CONFIG_PREEMPT_DESKTOP?
> >
> > [ 16.450000] ------------[ cut here ]------------
> > [ 16.450000] WARNING: at /work/rt/linux-2.6.33-rt/kernel/mutex-debug.c:65 mutex_remove_waiter+0xe8/0x11c()
> > [ 16.450000] Modules linked in:
> > [ 16.450000] [<c0033e68>] (unwind_backtrace+0x0/0xdc) from [<c0324994>] (dump_stack+0x18/0x1c)
> > [ 16.450000] [<c0324994>] (dump_stack+0x18/0x1c) from [<c0049aec>] (warn_slowpath_common+0x50/0x68)
> > [ 16.450000] [<c0049aec>] (warn_slowpath_common+0x50/0x68) from [<c0049b1c>] (warn_slowpath_null+0x18/0x1c)
> > [ 16.450000] [<c0049b1c>] (warn_slowpath_null+0x18/0x1c) from [<c006d640>] (mutex_remove_waiter+0xe8/0x11c)
> > [ 16.450000] [<c006d640>] (mutex_remove_waiter+0xe8/0x11c) from [<c032709c>] (mutex_lock_nested+0x268/0x304)
> > [ 16.450000] [<c032709c>] (mutex_lock_nested+0x268/0x304) from [<c004a2d8>] (acquire_console_mutex+0x40/0x68)
> > [ 16.450000] [<c004a2d8>] (acquire_console_mutex+0x40/0x68) from [<c01d8420>] (con_open+0x18/0xc4)
> > [ 16.450000] [<c01d8420>] (con_open+0x18/0xc4) from [<c01c80dc>] (tty_open+0x398/0x55c)
> > [ 16.450000] [<c01c80dc>] (tty_open+0x398/0x55c) from [<c00ae628>] (chrdev_open+0x198/0x1bc)
> > [ 16.450000] [<c00ae628>] (chrdev_open+0x198/0x1bc) from [<c00a9928>] (__dentry_open+0x188/0x294)
> > [ 16.450000] [<c00a9928>] (__dentry_open+0x188/0x294) from [<c00a9b04>] (nameidata_to_filp+0x48/0x60)
> > [ 16.450000] [<c00a9b04>] (nameidata_to_filp+0x48/0x60) from [<c00b795c>] (do_filp_open+0x42c/0x8a8)
> > [ 16.450000] [<c00b795c>] (do_filp_open+0x42c/0x8a8) from [<c00a968c>] (do_sys_open+0x64/0x11c)
> > [ 16.450000] [<c00a968c>] (do_sys_open+0x64/0x11c) from [<c00a977c>] (sys_open+0x24/0x28)
> > [ 16.450000] [<c00a977c>] (sys_open+0x24/0x28) from [<c002e000>] (ret_fast_syscall+0x0/0x34)
> > [ 16.450000] ---[ end trace cdbe849ecfa1acdf ]---
> >
> > The used config is shown after dmesg.
>
> As a wild guess, this might happen because we drop the BKL in
> mutex_lock_nested and might need to wait for it when we got the lock.
> The reason that this surfaces in -rt would be that the console_sem
> is replaced with a proper mutex there, on non-rt kernels this would
> be invisible.
>
> You could try to pull in the blk/tty branch from
> http://git.kernel.org/?p=linux/kernel/git/arnd/playground.git and enable
> CONFIG_TTY_MUTEX to see if that gives you better lockdep output,
> because that replaces the implicit dropping of the BKL with mutex operations
> that lockdep is aware of.
CONFIG_TTY_MUTEX depends on SMP and this ARM system does not support
CONFIG_SMP, its hidden by Kconfig dependencies.
Olaf
next prev parent reply other threads:[~2010-05-30 21:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-24 22:53 acquire_console_mutex: WARNING: at 2.6.33.4-rt20/kernel/mutex-debug.c:65 mutex_remove_waiter+0xe8/0x11c() Olaf Hering
2010-05-25 11:18 ` Arnd Bergmann
2010-05-30 21:39 ` Olaf Hering [this message]
2010-05-31 11:29 ` Arnd Bergmann
2010-06-02 9:13 ` Olaf Hering
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=20100530213902.GA3619@aepfle.de \
--to=olaf@aepfle.de \
--cc=arnd@arndb.de \
--cc=linux-kernel@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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.