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Subject[PATCH]: use spin_lock_irqsave in try_one_irq()
(Prarit: Second try at this one, not sure if this made it to LKML or not.
Sending to a wider audience this time)

Booting 2.6.32-rc5 on some IBM systems results in

Disabling IRQ #19

=================================
[ INFO: inconsistent lock state ]
2.6.32-rc5 #1
---------------------------------
inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
swapper/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
(&irq_desc_lock_class){?.-...}, at: [<ffffffff810c264e>] try_one_irq+0x32/0x138
{IN-HARDIRQ-W} state was registered at:
[<ffffffff81095160>] __lock_acquire+0x2fc/0xd5d
[<ffffffff81095cb4>] lock_acquire+0xf3/0x12d
[<ffffffff814cdadd>] _spin_lock+0x40/0x89
[<ffffffff810c3389>] handle_level_irq+0x30/0x105
[<ffffffff81014e0e>] handle_irq+0x95/0xb7
[<ffffffff810141bd>] do_IRQ+0x6a/0xe0
[<ffffffff81012813>] ret_from_intr+0x0/0x16
irq event stamp: 195096
hardirqs last enabled at (195096): [<ffffffff814cd7f7>] _spin_unlock_irq+0x3a/0x5c
hardirqs last disabled at (195095): [<ffffffff814cdbdd>] _spin_lock_irq+0x29/0x95
softirqs last enabled at (195088): [<ffffffff81068c92>] __do_softirq+0x1c1/0x1ef
softirqs last disabled at (195093): [<ffffffff8101304c>] call_softirq+0x1c/0x30

other info that might help us debug this:
1 lock held by swapper/0:
#0: (kernel/irq/spurious.c:21){+.-...}, at: [<ffffffff81070cf2>] run_timer_softirq+0x1a9/0x315

stack backtrace:
Pid: 0, comm: swapper Not tainted 2.6.32-rc5 #1
Call Trace:
<IRQ> [<ffffffff81093e94>] valid_state+0x187/0x1ae
[<ffffffff81096c7b>] ? check_usage_backwards+0x0/0xa3
[<ffffffff81093fe4>] mark_lock+0x129/0x253
[<ffffffff810951d4>] __lock_acquire+0x370/0xd5d
[<ffffffff810c264e>] ? try_one_irq+0x32/0x138
[<ffffffff8109329d>] ? save_trace+0x4e/0xcd
[<ffffffff81095cb4>] lock_acquire+0xf3/0x12d
[<ffffffff810c264e>] ? try_one_irq+0x32/0x138
[<ffffffff81070cf2>] ? run_timer_softirq+0x1a9/0x315
[<ffffffff810c264e>] ? try_one_irq+0x32/0x138
[<ffffffff814cdadd>] _spin_lock+0x40/0x89
[<ffffffff810c264e>] ? try_one_irq+0x32/0x138
[<ffffffff810c264e>] try_one_irq+0x32/0x138
[<ffffffff810c2795>] poll_all_shared_irqs+0x41/0x6d
[<ffffffff810c27dd>] poll_spurious_irqs+0x1c/0x49
[<ffffffff81070d82>] run_timer_softirq+0x239/0x315
[<ffffffff81070cf2>] ? run_timer_softirq+0x1a9/0x315
[<ffffffff810c27c1>] ? poll_spurious_irqs+0x0/0x49
[<ffffffff81068bd3>] __do_softirq+0x102/0x1ef
[<ffffffff8108eccf>] ? tick_dev_program_event+0x46/0xcc
[<ffffffff8101304c>] call_softirq+0x1c/0x30
[<ffffffff81014b65>] do_softirq+0x59/0xca
[<ffffffff810686ad>] irq_exit+0x58/0xae
[<ffffffff81029b84>] smp_apic_timer_interrupt+0x94/0xba
[<ffffffff81012a33>] apic_timer_interrupt+0x13/0x20
<EOI> [<ffffffff8101a7b5>] ? mwait_idle+0x8c/0xb5
[<ffffffff8101a7ac>] ? mwait_idle+0x83/0xb5
[<ffffffff81010e55>] ? cpu_idle+0xbe/0x100
[<ffffffff814c4270>] ? start_secondary+0x219/0x270

This happens because the &desc->lock is taken with spin_lock_irqsave and
just a spin_lock. In the try_one_irq(), this lock really should be a
spin_lock_irqsave().

I have not yet narrowed down the reason for the spurious interrupt (although
I suspect it maybe to do with the radeon driver).

Successfully tested by me.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>

--- linux-2.6.31.x86_64.orig/kernel/irq/spurious.c 2009-09-09 18:13:59.000000000 -0400
+++ linux-2.6.31.x86_64/kernel/irq/spurious.c 2009-10-26 10:55:56.709845786 -0400
@@ -27,8 +27,9 @@ static int try_one_irq(int irq, struct i
{
struct irqaction *action;
int ok = 0, work = 0;
+ unsigned long flags;

- spin_lock(&desc->lock);
+ spin_lock_irqsave(&desc->lock, flags);
/* Already running on another processor */
if (desc->status & IRQ_INPROGRESS) {
/*
@@ -37,13 +38,13 @@ static int try_one_irq(int irq, struct i
*/
if (desc->action && (desc->action->flags & IRQF_SHARED))
desc->status |= IRQ_PENDING;
- spin_unlock(&desc->lock);
+ spin_unlock_irqrestore(&desc->lock, flags);
return ok;
}
/* Honour the normal IRQ locking */
desc->status |= IRQ_INPROGRESS;
action = desc->action;
- spin_unlock(&desc->lock);
+ spin_unlock_irqrestore(&desc->lock, flags);

while (action) {
/* Only shared IRQ handlers are safe to call */
@@ -56,7 +57,7 @@ static int try_one_irq(int irq, struct i
}
local_irq_disable();
/* Now clean up the flags */
- spin_lock(&desc->lock);
+ spin_lock_irqsave(&desc->lock, flags);
action = desc->action;

/*
@@ -68,9 +69,9 @@ static int try_one_irq(int irq, struct i
* Perform real IRQ processing for the IRQ we deferred
*/
work = 1;
- spin_unlock(&desc->lock);
+ spin_unlock_irqrestore(&desc->lock, flags);
handle_IRQ_event(irq, action);
- spin_lock(&desc->lock);
+ spin_lock_irqsave(&desc->lock, flags);
desc->status &= ~IRQ_PENDING;
}
desc->status &= ~IRQ_INPROGRESS;
@@ -80,7 +81,7 @@ static int try_one_irq(int irq, struct i
*/
if (work && desc->chip && desc->chip->end)
desc->chip->end(irq);
- spin_unlock(&desc->lock);
+ spin_unlock_irqrestore(&desc->lock, flags);

return ok;
}

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