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From: Anupam Kapoor <anupam.kapoor@gmail.com>
To: kernel-janitors@vger.kernel.org
Subject: [Kernel-janitors] doubt in drivers/usb/class/audio.c
Date: Thu, 01 Jul 2004 13:22:49 +0000	[thread overview]
Message-ID: <e3177630407010610608b87e9@mail.gmail.com> (raw)

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hi, 

while checking the above file for proper usage of set_current_state, i
came accross the following fragment (at approx line 2670) in
drivers/usb/class/audio.c:usb_audio_open()

	__set_current_state(TASK_INTERRUPTIBLE);
        add_wait_queue(&open_wait, &wait);

the problem here (imho) is that, it is possible that the
current->state write is re-ordered after the process was added to the
wait queue. if the task gets woken up in between those events, then we
have a problem.

so what actually happens is

add_wait_queue(&open_wait, &wait);
<the task get's woken up here>
__set_current_state(TASK_INTERRUPTIBLE);

now we are in a big sleep.

i think __set_current_state should just be replaced with
set_current_state which provides the appropriate memory barrier ?

kind regards
anupam

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                 reply	other threads:[~2004-07-01 13:22 UTC|newest]

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