From: Peter Hurley <peter@hurleysoftware.com>
To: John Ogness <john.ogness@linutronix.de>, linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Tony Lindgren <tony@atomide.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-omap@vger.kernel.org, nsekhar@ti.com, nm@ti.com,
linux-serial@vger.kernel.org
Subject: Re: [PATCH 1/3] serial: 8250: unlock port for uart_write_wakeup()
Date: Thu, 30 Jul 2015 19:15:23 -0400 [thread overview]
Message-ID: <55BAB00B.3010806@hurleysoftware.com> (raw)
In-Reply-To: <87h9ol2r4y.fsf@linutronix.de>
On 07/30/2015 06:54 PM, John Ogness wrote:
> uart_write_wakeup() should be called without holding the port lock.
> Otherwise a possible recursive spinlock issue can occur, such as
> the following callchain:
>
> 8250_core.c:serial8250_tx_chars() - called with port locked
> serial_core.c:uart_write_wakeup()
> tty_io.c:tty_wakeup()
> st_core.c:st_tty_wakeup()
> st_core.c:st_tx_wakeup()
> st_core.c:st_int_write()
> serial_core.c:uart_write() - locks port
NAK.
This is a bug in the N_TI_WL line discipline, specifically in the
st_tx_wakeup() function, which cannot perform the write synchronously.
This is a common line discipline bug, and typically fixed by performing
the wakeup operations from a kworker instead.
Regards,
Peter Hurley
next prev parent reply other threads:[~2015-07-30 23:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-30 22:54 [PATCH 1/3] serial: 8250: unlock port for uart_write_wakeup() John Ogness
2015-07-30 23:15 ` Peter Hurley [this message]
2015-07-30 23:53 ` Peter Hurley
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