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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Qian Cai <cai@lca.pw>
Cc: pmladek@suse.com, tytso@mit.edu,
	sergey.senozhatsky.work@gmail.com, Arnd Bergmann <arnd@arndb.de>,
	peterz@infradead.org, gregkh@linuxfoundation.org,
	linux-kernel@vger.kernel.org, rostedt@goodmis.org,
	linux-mm@kvack.org, Catalin Marinas <catalin.marinas@arm.com>,
	longman@redhat.com, dan.j.williams@intel.com, will@kernel.org,
	tglx@linutronix.de, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] char/random: silence a lockdep splat with printk()
Date: Thu, 5 Dec 2019 10:00:55 +0900	[thread overview]
Message-ID: <20191205010055.GO93017@google.com> (raw)
In-Reply-To: <637027D4-BBDD-4AA6-B03C-556060988957@lca.pw>

Hi,

On (19/12/03 13:46), Qian Cai wrote:
> > On Nov 13, 2019, at 4:16 PM, Qian Cai <cai@lca.pw> wrote:
> > 
> > From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> > 
> > Sergey didn't like the locking order,
> > 
> > uart_port->lock  ->  tty_port->lock
> > 
> > uart_write (uart_port->lock)
> >  __uart_start
> >    pl011_start_tx
> >      pl011_tx_chars
> >        uart_write_wakeup
> >          tty_port_tty_wakeup
> >            tty_port_default
> >              tty_port_tty_get (tty_port->lock)
> > 
> > but those code is so old, and I have no clue how to de-couple it after
> > checking other locks in the splat. There is an onging effort to make all
> > printk() as deferred, so until that happens, workaround it for now as a
> > short-term fix.
> 
> Sergey, could we have a ACK from you so Ted might be able to merge?

Not sure if I can ACK it, but overall it makes sense to use deferred
printk there.

[..]
> 
> > [cai@lca.pw: add a commit log.]
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> > Signed-off-by: Qian Cai <cai@lca.pw>
> > ---
> > 
> > Sergey, please let us know if you are fine with the Signed-off-by.

A 'Reviewed-by' will suffice.

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

	-ss

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WARNING: multiple messages have this Message-ID (diff)
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Qian Cai <cai@lca.pw>
Cc: tytso@mit.edu, Arnd Bergmann <arnd@arndb.de>,
	gregkh@linuxfoundation.org, sergey.senozhatsky.work@gmail.com,
	pmladek@suse.com, rostedt@goodmis.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	will@kernel.org, dan.j.williams@intel.com, peterz@infradead.org,
	longman@redhat.com, tglx@linutronix.de, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] char/random: silence a lockdep splat with printk()
Date: Thu, 5 Dec 2019 10:00:55 +0900	[thread overview]
Message-ID: <20191205010055.GO93017@google.com> (raw)
In-Reply-To: <637027D4-BBDD-4AA6-B03C-556060988957@lca.pw>

Hi,

On (19/12/03 13:46), Qian Cai wrote:
> > On Nov 13, 2019, at 4:16 PM, Qian Cai <cai@lca.pw> wrote:
> > 
> > From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> > 
> > Sergey didn't like the locking order,
> > 
> > uart_port->lock  ->  tty_port->lock
> > 
> > uart_write (uart_port->lock)
> >  __uart_start
> >    pl011_start_tx
> >      pl011_tx_chars
> >        uart_write_wakeup
> >          tty_port_tty_wakeup
> >            tty_port_default
> >              tty_port_tty_get (tty_port->lock)
> > 
> > but those code is so old, and I have no clue how to de-couple it after
> > checking other locks in the splat. There is an onging effort to make all
> > printk() as deferred, so until that happens, workaround it for now as a
> > short-term fix.
> 
> Sergey, could we have a ACK from you so Ted might be able to merge?

Not sure if I can ACK it, but overall it makes sense to use deferred
printk there.

[..]
> 
> > [cai@lca.pw: add a commit log.]
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> > Signed-off-by: Qian Cai <cai@lca.pw>
> > ---
> > 
> > Sergey, please let us know if you are fine with the Signed-off-by.

A 'Reviewed-by' will suffice.

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

	-ss


  reply	other threads:[~2019-12-05  1:01 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-13 21:16 [PATCH] char/random: silence a lockdep splat with printk() Qian Cai
2019-11-13 21:16 ` Qian Cai
2019-12-03 18:46 ` Qian Cai
2019-12-03 18:46   ` Qian Cai
2019-12-05  1:00   ` Sergey Senozhatsky [this message]
2019-12-05  1:00     ` Sergey Senozhatsky
2019-12-17  1:52     ` Qian Cai
2019-12-17  1:52       ` Qian Cai
2020-01-02 15:42       ` Qian Cai
2020-01-02 15:42         ` Qian Cai
2020-01-02 17:07         ` Steven Rostedt
2020-01-02 17:07           ` Steven Rostedt
2020-01-02 17:16           ` Qian Cai
2020-01-02 17:16             ` Qian Cai
2020-01-02 18:00         ` Theodore Y. Ts'o
2020-01-02 18:00           ` Theodore Y. Ts'o
2020-01-07 21:07 ` Theodore Y. Ts'o
2020-01-07 21:07   ` Theodore Y. Ts'o
2020-03-24 15:13 ` dmesg -w regression in v5.4.22, bisected, was: " Zygo Blaxell
2020-03-24 15:13   ` Zygo Blaxell
2020-03-25  2:35   ` Sergey Senozhatsky
2020-03-25  2:35     ` Sergey Senozhatsky

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