linux-kernel - Re: [RFC][PATCH 5/7] tty: Deal with nested sleeps

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Message-ID: <20140805232916.GC26505@kroah.com>
Date:	Tue, 5 Aug 2014 16:29:16 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...nel.org, oleg@...hat.com, torvalds@...ux-foundation.org,
	tglx@...utronix.de, ilya.dryomov@...tank.com,
	umgwanakikbuti@...il.com, linux-kernel@...r.kernel.org,
	Jiri Slaby <jslaby@...e.cz>
Subject: Re: [RFC][PATCH 5/7] tty: Deal with nested sleeps

On Mon, Aug 04, 2014 at 12:30:30PM +0200, Peter Zijlstra wrote:
> n_tty_{read,write} are wait loops with sleeps in. Wait loops rely on
> task_struct::state and sleeps do too, since that's the only means of
> actually sleeping. Therefore the nested sleeps destroy the wait loop
> state and the wait loop breaks the sleep functions that assume
> TASK_RUNNING (mutex_lock).
> 
> Fix this by using the new woken_wake_function and wait_woken() stuff,
> which registers wakeups in wait and thereby allows shrinking the
> task_state::state changes to the actual sleep part.
> 
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Jiri Slaby <jslaby@...e.cz>
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> ---
>  drivers/tty/n_tty.c |   17 +++++------------
>  1 file changed, 5 insertions(+), 12 deletions(-)
> 

Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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