linux-kernel - BUG? possible race between tasklet_action and tasklet

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Message-ID: <4AAA8213.8070008@nortel.com>
Date:	Fri, 11 Sep 2009 11:00:03 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	Linux kernel <linux-kernel@...r.kernel.org>
Subject: BUG?  possible race between tasklet_action and tasklet_kill

I think I may have discovered a race between tasklet_action and
tasklet_kill.  Given how long this code has been around, I assume that
I'm simply not understanding the purposes of tasklet_kill correctly, but
it seems like there's a mechanism whereby we could hit the BUG path in
tasklet_action().

cpu A                             cpu B
starts tasklet_kill()
does while loop until
  TASKLET_STATE_SCHED not set
                                  runs tasklet_schedule()
                                  starts tasklet_action()
tasklet_unlock_wait()
                                  if (tasklet_trylock(t)) {
clear_bit(TASKLET_STATE_SCHED)
                                  test_and_clear_bit(TASKLET_STATE_SCHED
                                  BUG

Is this a valid issue, or is this an improper usage pattern somehow?

Thanks,

Chris
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