Messages in this thread Patches in this message | | | Date | Fri, 23 Dec 2011 16:35:21 -0500 | From | Karandeep Chahal <> | Subject | [PATCH] sb_edac.c, kernel linux-3.2-rc6. |
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While testing Sandy Bridge EDAC module I discovered a problem in the way sb_edac was registering itself for machine check notifications. The symptoms of the problem include: 1. Injecting a machine check exception can cause the system to hang for 10-15 seconds. 2. Removing and re-inserting the kernel module can cause panic.
The system hangs for 10-15 seconds because the sb_edac notifier gets called by the kernel (notifier_call_chain) 0xffffffff times ((u32)(-1)).
The problem occurs because sb_edac calls atomic_notifier_chain_register twice with the same static notifier_block structure. The function atomic_notifier_chain_register gets called once for each memory controller (MC) with the same structure. The patch, then, fixes this problem by making sure that sb_edac registers for machine check notifications only once.
Also copying Mauro Carvalho Chehab (maintainer of sb_edac) for the review of the patch.
Cheers, Karan
--- linux-3.2-rc6/drivers/edac/sb_edac.c 2011-12-16 21:36:26.000000000 -0500 +++ linux-3.2-rc6-new/drivers/edac/sb_edac.c 2011-12-23 14:54:57.000000000 -0500 @@ -1661,9 +1661,6 @@ debugf0("MC: " __FILE__ ": %s(): mci = %p, dev = %p\n", __func__, mci, &sbridge_dev->pdev[0]->dev);
- atomic_notifier_chain_unregister(&x86_mce_decoder_chain, - &sbridge_mce_dec); - /* Remove MC sysfs nodes */ edac_mc_del_mc(mci->dev);
@@ -1731,8 +1728,6 @@ goto fail0; }
- atomic_notifier_chain_register(&x86_mce_decoder_chain, - &sbridge_mce_dec); return 0;
fail0: @@ -1861,8 +1856,11 @@
pci_rc = pci_register_driver(&sbridge_driver);
- if (pci_rc >= 0) + if (pci_rc >= 0) { + atomic_notifier_chain_register(&x86_mce_decoder_chain, + &sbridge_mce_dec); return 0; + }
sbridge_printk(KERN_ERR, "Failed to register device with error %d.\n", pci_rc); @@ -1877,6 +1875,9 @@ static void __exit sbridge_exit(void) { debugf2("MC: " __FILE__ ": %s()\n", __func__); + atomic_notifier_chain_unregister(&x86_mce_decoder_chain, + &sbridge_mce_dec); + pci_unregister_driver(&sbridge_driver); }
--- linux-3.2-rc6/drivers/edac/sb_edac.c 2011-12-16 21:36:26.000000000 -0500 +++ linux-3.2-rc6-new/drivers/edac/sb_edac.c 2011-12-23 14:54:57.000000000 -0500 @@ -1661,9 +1661,6 @@ debugf0("MC: " __FILE__ ": %s(): mci = %p, dev = %p\n", __func__, mci, &sbridge_dev->pdev[0]->dev); - atomic_notifier_chain_unregister(&x86_mce_decoder_chain, - &sbridge_mce_dec); - /* Remove MC sysfs nodes */ edac_mc_del_mc(mci->dev); @@ -1731,8 +1728,6 @@ goto fail0; } - atomic_notifier_chain_register(&x86_mce_decoder_chain, - &sbridge_mce_dec); return 0; fail0: @@ -1861,8 +1856,11 @@ pci_rc = pci_register_driver(&sbridge_driver); - if (pci_rc >= 0) + if (pci_rc >= 0) { + atomic_notifier_chain_register(&x86_mce_decoder_chain, + &sbridge_mce_dec); return 0; + } sbridge_printk(KERN_ERR, "Failed to register device with error %d.\n", pci_rc); @@ -1877,6 +1875,9 @@ static void __exit sbridge_exit(void) { debugf2("MC: " __FILE__ ": %s()\n", __func__); + atomic_notifier_chain_unregister(&x86_mce_decoder_chain, + &sbridge_mce_dec); + pci_unregister_driver(&sbridge_driver); } [PATCH] sb_edac.c, kernel linux-3.2-rc6. Karandeep Chahal <karandeepchahal@gmail.com>
The sb_edac patch fixes incorrect Sandy Bridge machine check notifier chain registration problem.
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