releases/2.6.32.17/genirq-deal-with-desc-set_type-changing-desc-chip.patch

   1 From 4673247562e39a17e09440fa1400819522ccd446 Mon Sep 17 00:00:00 2001
   2 From: Thomas Gleixner <tglx@linutronix.de>
   3 Date: Mon, 7 Jun 2010 17:53:51 +0200
   4 Subject: genirq: Deal with desc->set_type() changing desc->chip
   5
   6 From: Thomas Gleixner <tglx@linutronix.de>
   7
   8 commit 4673247562e39a17e09440fa1400819522ccd446 upstream.
   9
  10 The set_type() function can change the chip implementation when the
  11 trigger mode changes. That might result in using an non-initialized
  12 irq chip when called from __setup_irq() or when called via
  13 set_irq_type() on an already enabled irq.
  14
  15 The set_irq_type() function should not be called on an enabled irq,
  16 but because we forgot to put a check into it, we have a bunch of users
  17 which grew the habit of doing that and it never blew up as the
  18 function is serialized via desc->lock against all users of desc->chip
  19 and they never hit the non-initialized irq chip issue.
  20
  21 The easy fix for the __setup_irq() issue would be to move the
  22 irq_chip_set_defaults(desc->chip) call after the trigger setting to
  23 make sure that a chip change is covered.
  24
  25 But as we have already users, which do the type setting after
  26 request_irq(), the safe fix for now is to call irq_chip_set_defaults()
  27 from __irq_set_trigger() when desc->set_type() changed the irq chip.
  28
  29 It needs a deeper analysis whether we should refuse to change the chip
  30 on an already enabled irq, but that'd be a large scale change to fix
  31 all the existing users. So that's neither stable nor 2.6.35 material.
  32
  33 Reported-by: Esben Haabendal <eha@doredevelopment.dk>
  34 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  35 Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
  36 Cc: linuxppc-dev <linuxppc-dev@ozlabs.org>
  37 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  38
  39 ---
  40  kernel/irq/manage.c |    3 +++
  41  1 file changed, 3 insertions(+)
  42
  43 --- a/kernel/irq/manage.c
  44 +++ b/kernel/irq/manage.c
  45 @@ -436,6 +436,9 @@ int __irq_set_trigger(struct irq_desc *d
  46                 /* note that IRQF_TRIGGER_MASK == IRQ_TYPE_SENSE_MASK */
  47                 desc->status &= ~(IRQ_LEVEL | IRQ_TYPE_SENSE_MASK);
  48                 desc->status |= flags;
  49 +
  50 +               if (chip != desc->chip)
  51 +                       irq_chip_set_defaults(desc->chip);
  52         }
  53
  54         return ret;