[PATCH] sb_edac: Only register mce_decode_chain once

[Roland Dreier <roland@kernel.org>]

From: Roland Dreier <roland@purestorage.com>

I was lucky enough to get a 4-socket Sandy Bridge system.
Unfortunately it hangs on boot when loading the sb_edac module, with
the NMI watchdog giving the following trace:

    EDAC MC0: Giving out device to 'sbridge_edac.c' 'Sandy Bridge Socket#0': DEV 0000:3f:0e.0
    EDAC MC1: Giving out device to 'sbridge_edac.c' 'Sandy Bridge Socket#1': DEV 0000:7f:0e.0
    EDAC MC2: Giving out device to 'sbridge_edac.c' 'Sandy Bridge Socket#2': DEV 0000:bf:0e.0
    ------------[ cut here ]------------
    WARNING: at /home/roland/linux-2.6/kernel/watchdog.c:242 watchdog_overflow_callback+0x9a/0xc0()
    Hardware name:
    Watchdog detected hard LOCKUP on cpu 11
    Modules linked in: sb_edac(+) edac_core kvm_intel coretemp kvm mei acpi_pad joydev ghash_clmulni_intel hid_generic aesni_intel cryptd aes_x86_64 acpi_power_meter lpc_ich shpchp microcode usbhid hid ses enclosure bnx2x libcrc32c megaraid_sas mdio
    Pid: 2408, comm: modprobe Tainted: G        W    3.4.0+ #1
    Call Trace:
     <NMI>  [<ffffffff810515ff>] warn_slowpath_common+0x7f/0xc0
     [<ffffffff810516f6>] warn_slowpath_fmt+0x46/0x50
     [<ffffffff810db3da>] watchdog_overflow_callback+0x9a/0xc0
     [<ffffffff81115ffc>] __perf_event_overflow+0x9c/0x220
     [<ffffffff81024faa>] ? x86_perf_event_set_period+0xda/0x150
     [<ffffffff81116ad4>] perf_event_overflow+0x14/0x20
     [<ffffffff8102a190>] intel_pmu_handle_irq+0x180/0x300
     [<ffffffff813a0ed0>] ? ghes_read_estatus+0x90/0x180
     [<ffffffff816550d1>] perf_event_nmi_handler+0x21/0x30
     [<ffffffff81654851>] nmi_handle.isra.0+0x51/0x80
     [<ffffffff81654a21>] do_nmi+0x1a1/0x380
     [<ffffffff81653e7c>] end_repeat_nmi+0x1a/0x1e
     [<ffffffff8107aa05>] ? atomic_notifier_chain_register+0x35/0x60
     [<ffffffff8107aa05>] ? atomic_notifier_chain_register+0x35/0x60
     [<ffffffff8107aa05>] ? atomic_notifier_chain_register+0x35/0x60
     <<EOE>>  [<ffffffff8102b5dd>] mce_register_decode_chain+0x2d/0x120
     [<ffffffffa00fdbdb>] sbridge_probe+0xa86/0xbab [sb_edac]
     [<ffffffff811eaf05>] ? sysfs_link_sibling+0xa5/0xe0
     [<ffffffff81339c1c>] local_pci_probe+0x5c/0xd0
     [<ffffffff8133b551>] pci_device_probe+0x101/0x120
     [<ffffffff813fbf3e>] driver_probe_device+0x7e/0x220
     [<ffffffff813fc18b>] __driver_attach+0xab/0xb0
     [<ffffffff813fc0e0>] ? driver_probe_device+0x220/0x220
     [<ffffffff813fa376>] bus_for_each_dev+0x56/0x90
     [<ffffffff813fba5e>] driver_attach+0x1e/0x20
     [<ffffffff813fb610>] bus_add_driver+0x1a0/0x270
     [<ffffffffa000a000>] ? 0xffffffffa0009fff
     [<ffffffffa000a000>] ? 0xffffffffa0009fff
     [<ffffffff813fc6e6>] driver_register+0x76/0x130
     [<ffffffffa000a000>] ? 0xffffffffa0009fff
     [<ffffffff8133b225>] __pci_register_driver+0x55/0xd0
     [<ffffffffa000a033>] sbridge_init+0x33/0x1000 [sb_edac]
     [<ffffffff8100203f>] do_one_initcall+0x3f/0x170
     [<ffffffff810b2c0e>] sys_init_module+0xbe/0x230
     [<ffffffff8165b7a9>] system_call_fastpath+0x16/0x1b
    ---[ end trace a7919e7f17c0a727 ]---

The problem is that the system has multiple memory controllers but
registers the same static notifier_block multiple times.  Fix this by
moving the registration/unregistration to the module init/exit function.

Cc: <stable@vger.kernel.org>
Signed-off-by: Roland Dreier <roland@purestorage.com>
---
 drivers/edac/sb_edac.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/edac/sb_edac.c b/drivers/edac/sb_edac.c
index 4adaf4b..a21ace0 100644
--- a/drivers/edac/sb_edac.c
+++ b/drivers/edac/sb_edac.c
@@ -1604,8 +1604,6 @@ static void sbridge_unregister_mci(struct sbridge_dev *sbridge_dev)
 	debugf0("MC: " __FILE__ ": %s(): mci = %p, dev = %p\n",
 		__func__, mci, &sbridge_dev->pdev[0]->dev);
 
-	mce_unregister_decode_chain(&sbridge_mce_dec);
-
 	/* Remove MC sysfs nodes */
 	edac_mc_del_mc(mci->dev);
 
@@ -1682,7 +1680,6 @@ static int sbridge_register_mci(struct sbridge_dev *sbridge_dev)
 		goto fail0;
 	}
 
-	mce_register_decode_chain(&sbridge_mce_dec);
 	return 0;
 
 fail0:
@@ -1811,8 +1808,10 @@ static int __init sbridge_init(void)
 
 	pci_rc = pci_register_driver(&sbridge_driver);
 
-	if (pci_rc >= 0)
+	if (pci_rc >= 0) {
+		mce_register_decode_chain(&sbridge_mce_dec);
 		return 0;
+	}
 
 	sbridge_printk(KERN_ERR, "Failed to register device with error %d.\n",
 		      pci_rc);
@@ -1828,6 +1827,7 @@ static void __exit sbridge_exit(void)
 {
 	debugf2("MC: " __FILE__ ": %s()\n", __func__);
 	pci_unregister_driver(&sbridge_driver);
+	mce_unregister_decode_chain(&sbridge_mce_dec);
 }
 
 module_init(sbridge_init);
-- 
1.7.9.5