linux-kernel - Lots of bugs with current->state = TASK

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Date:	Tue, 19 Jan 2010 15:29:38 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	kernel-janitors <kernel-janitors@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arch@...r.kernel.org, Greg KH <greg@...ah.com>,
	Andy Whitcroft <apw@...onical.com>
Subject: Lots of bugs with current->state = TASK_*INTERRUPTIBLE

Peter Zijlstra and I were doing a look over of places that assign
current->state = TASK_*INTERRUPTIBLE, by simply looking at places with:

 $ git grep -A1 'state[[:space:]]*=[[:space:]]*TASK_[^R]'

and it seems there are quite a few places that looks like bugs. To be on
the safe side, everything outside of a run queue lock that sets the
current state to something other than TASK_RUNNING (or dead) should be
using set_current_state().

	current->state = TASK_INTERRUPTIBLE;
	schedule();

is probably OK, but it would not hurt to be consistent. Here's a few
examples of likely bugs:

>>From drivers/staging/line6/midi.c:

        current->state = TASK_INTERRUPTIBLE;

        while (line6->line6midi->num_active_send_urbs > 0)

>>From drivers/staging/line6/pod.c:

        current->state = TASK_INTERRUPTIBLE;

        while (param->value == POD_system_invalid) {

Also drivers/macintosh/adb.c looks like there's a bug too.

I'm sure there's others but I stopped looking.

Anyway, this looks like a good janitorial work. Anything that assigns
state outside the rq locks to something other than TASK_RUNNING and that
is not before a schedule() (perhaps even those) should be converted to:

	set_current_task(<state>).

This probably should be checked in checkpatch.pl too, if it is not
already.

-- Steve

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