[SCSI] qla2xxx: make msix interrupt handler safe for irq

[SCSI] qla2xxx: make msix interrupt handler safe for irq

Yinghai has reported a lockdep warning on qla2xxx:

[   77.965784] WARNING: at kernel/lockdep.c:2332
trace_hardirqs_on_caller+0xc6/0x14b()
[   77.977492] Hardware name: Sun
[   77.979485] Modules linked in:
[   77.994337] Pid: 0, comm: swapper Not tainted
2.6.33-rc4-tip-yh-03949-g3a8e3f5-dirty #64
[   78.000120] Call Trace:
[   78.013298]  <IRQ>  [<ffffffff81076b54>] warn_slowpath_common+0x7c/0x94
[   78.017746]  [<ffffffff81cd712c>] ? _raw_spin_unlock_irq+0x30/0x36
[   78.035171]  [<ffffffff81076b80>] warn_slowpath_null+0x14/0x16
[   78.040152]  [<ffffffff810a2ae8>] trace_hardirqs_on_caller+0xc6/0x14b
[   78.055400]  [<ffffffff810a2b7a>] trace_hardirqs_on+0xd/0xf
[   78.058951]  [<ffffffff81cd712c>] _raw_spin_unlock_irq+0x30/0x36
[   78.074889]  [<ffffffff816461ef>] qla24xx_msix_default+0x243/0x281
[   78.091598]  [<ffffffff810a5752>] ? __lock_release+0xa5/0xae
[   78.096799]  [<ffffffff810c02ae>] handle_IRQ_event+0x53/0x113
[   78.111568]  [<ffffffff810c2061>] handle_edge_irq+0xf3/0x13b
[   78.116255]  [<ffffffff81035109>] handle_irq+0x24/0x2f
[   78.132063]  [<ffffffff81cdc4b4>] do_IRQ+0x5c/0xc3
[   78.134684]  [<ffffffff81cd7393>] ret_from_intr+0x0/0xf
[   78.137903]  <EOI>  [<ffffffff81039a56>] ? mwait_idle+0xaf/0xbb
[   78.155674]  [<ffffffff81039a4d>] ? mwait_idle+0xa6/0xbb
[   78.158600]  [<ffffffff81031c7c>] cpu_idle+0x61/0xa1
[   78.174333]  [<ffffffff81c85d7a>] rest_init+0x7e/0x80
[   78.178122]  [<ffffffff82832d1f>] start_kernel+0x316/0x31d
[   78.193623]  [<ffffffff82832297>] x86_64_start_reservations+0xa7/0xab
[   78.198924]  [<ffffffff8283237f>] x86_64_start_kernel+0xe4/0xeb
[   78.214540] ---[ end trace be4529f30a2e4ef5 ]---

This was happened when qla2xxx msix interrupt handler is trying to enable
IRQs by spin_unlock_irq(). We should make interrupt handler safe for IRQs,
use spin_lock_irqsave/spin_unlock_irqrestore, this will not break the IRQs
status in interrupt handler.

Reported-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Acked-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>