Re: [PATCH] edac: avoid mce decoding crash after edac driver unloaded

[Chen Gong <gong.chen@linux.intel.com>]

锟斤拷 2012/5/5 9:20, Chen Gong 写锟斤拷:
> Some edac drivers register themselves as mce decoders via
> notifier_chain. But in current notifier_chain implementation logic,
> it doesn't accept same notifier registered twice. If so, it will be
> wrong when removing the element from the list. For example, on one
> SandyBridge platform, remove module sb_edac and then trigger one
> error, it will hit oops because it has no mce decoder registered
> but related notifier_chain still points to an invalid callback
> function. Here is an example:
>
> Call Trace:
>  [<ffffffff8150ef6a>] atomic_notifier_call_chain+0x1a/0x20
>  [<ffffffff8102b936>] mce_log+0x46/0x180
>  [<ffffffff8102eaea>] apei_mce_report_mem_error+0x4a/0x60
>  [<ffffffff812e19d2>] ghes_do_proc+0x192/0x210
>  [<ffffffff812e2066>] ghes_proc+0x46/0x70
>  [<ffffffff812e20d8>] ghes_notify_sci+0x48/0x80
>  [<ffffffff8150ef05>] notifier_call_chain+0x55/0x80
>  [<ffffffff81076f1a>] __blocking_notifier_call_chain+0x5a/0x80
>  [<ffffffff812aea11>] ? acpi_os_wait_events_complete+0x23/0x23
>  [<ffffffff81076f56>] blocking_notifier_call_chain+0x16/0x20
>  [<ffffffff812ddc4d>] acpi_hed_notify+0x19/0x1b
>  [<ffffffff812b16bd>] acpi_device_notify+0x19/0x1b
>  [<ffffffff812beb38>] acpi_ev_notify_dispatch+0x67/0x7f
>  [<ffffffff812aea3a>] acpi_os_execute_deferred+0x29/0x36
>  [<ffffffff81069dc2>] process_one_work+0x132/0x450
>  [<ffffffff8106bbcb>] worker_thread+0x17b/0x3c0
>  [<ffffffff8106ba50>] ? manage_workers+0x120/0x120
>  [<ffffffff81070aee>] kthread+0x9e/0xb0
>  [<ffffffff81514724>] kernel_thread_helper+0x4/0x10
>  [<ffffffff81070a50>] ? kthread_freezable_should_stop+0x70/0x70
>  [<ffffffff81514720>] ? gs_change+0x13/0x13
> Code: f3 49 89 d4 45 85 ed 4d 89 c6 48 8b 0f 74 48 48 85 c9 75 17 eb 41
> 0f 1f 80 00 00 00 00 41 83 ed 01 4c 89 f9 74 22 4d 85 ff 74 1d <4c> 8b
> 79 08 4c 89 e2 48 89 de 48 89 cf ff 11 4d 85 f6 74 04 41
> RIP  [<ffffffff8150eef6>] notifier_call_chain+0x46/0x80
>  RSP <ffff88042868fb20>
> CR2: ffffffffa01af838
> ---[ end trace 0100930068e73e6f ]---
> BUG: unable to handle kernel paging request at fffffffffffffff8
> IP: [<ffffffff810705b0>] kthread_data+0x10/0x20
> PGD 1a0d067 PUD 1a0e067 PMD 0
> Oops: 0000 [#2] SMP
>
> Only i7core_edac and sb_edac have such issues because they have more
> than one memory controller which means they have to register mce
> decoder many times.
>
> Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
> ---
>  drivers/edac/i7core_edac.c |   12 ++++++++++--
>  drivers/edac/sb_edac.c     |   12 ++++++++++--
>  2 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/edac/i7core_edac.c b/drivers/edac/i7core_edac.c
> index 85226cc..1852a52 100644
> --- a/drivers/edac/i7core_edac.c
> +++ b/drivers/edac/i7core_edac.c
> @@ -2216,6 +2216,7 @@ static void i7core_unregister_mci(struct i7core_dev *i7core_dev)
>  {
>  	struct mem_ctl_info *mci = i7core_dev->mci;
>  	struct i7core_pvt *pvt;
> +	static int once;
>  
>  	if (unlikely(!mci || !mci->pvt_info)) {
>  		debugf0("MC: " __FILE__ ": %s(): dev = %p\n",
> @@ -2234,7 +2235,10 @@ static void i7core_unregister_mci(struct i7core_dev *i7core_dev)
>  	if (pvt->enable_scrub)
>  		disable_sdram_scrub_setting(mci);
>  
> -	mce_unregister_decode_chain(&i7_mce_dec);
> +	if (!once) {
> +		mce_unregister_decode_chain(&i7_mce_dec);
> +		once = 1;
> +	}
>  
>  	/* Disable EDAC polling */
>  	i7core_pci_ctl_release(pvt);
> @@ -2253,6 +2257,7 @@ static int i7core_register_mci(struct i7core_dev *i7core_dev)
>  	struct mem_ctl_info *mci;
>  	struct i7core_pvt *pvt;
>  	int rc, channels, csrows;
> +	static int once;
>  
>  	/* Check the number of active and not disabled channels */
>  	rc = i7core_get_active_channels(i7core_dev->socket, &channels, &csrows);
> @@ -2336,7 +2341,10 @@ static int i7core_register_mci(struct i7core_dev *i7core_dev)
>  	/* DCLK for scrub rate setting */
>  	pvt->dclk_freq = get_dclk_freq();
>  
> -	mce_register_decode_chain(&i7_mce_dec);
> +	if (!once) {
> +		mce_register_decode_chain(&i7_mce_dec);
> +		once = 1;
> +	}
>  
>  	return 0;
>  
> diff --git a/drivers/edac/sb_edac.c b/drivers/edac/sb_edac.c
> index a203536..20fabc8 100644
> --- a/drivers/edac/sb_edac.c
> +++ b/drivers/edac/sb_edac.c
> @@ -1655,6 +1655,7 @@ static void sbridge_unregister_mci(struct sbridge_dev *sbridge_dev)
>  {
>  	struct mem_ctl_info *mci = sbridge_dev->mci;
>  	struct sbridge_pvt *pvt;
> +	static int once;
>  
>  	if (unlikely(!mci || !mci->pvt_info)) {
>  		debugf0("MC: " __FILE__ ": %s(): dev = %p\n",
> @@ -1669,7 +1670,10 @@ 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);
> +	if (!once) {
> +		mce_unregister_decode_chain(&sbridge_mce_dec);
> +		once = 1;
> +	}
>  
>  	/* Remove MC sysfs nodes */
>  	edac_mc_del_mc(mci->dev);
> @@ -1685,6 +1689,7 @@ static int sbridge_register_mci(struct sbridge_dev *sbridge_dev)
>  	struct mem_ctl_info *mci;
>  	struct sbridge_pvt *pvt;
>  	int rc, channels, csrows;
> +	static int once;
>  
>  	/* Check the number of active and not disabled channels */
>  	rc = sbridge_get_active_channels(sbridge_dev->bus, &channels, &csrows);
> @@ -1738,7 +1743,10 @@ static int sbridge_register_mci(struct sbridge_dev *sbridge_dev)
>  		goto fail0;
>  	}
>  
> -	mce_register_decode_chain(&sbridge_mce_dec);
> +	if (!once) {
> +		mce_register_decode_chain(&sbridge_mce_dec);
> +		once = 1;
> +	}
>  	return 0;
>  
>  fail0:
IMO, function notifier_chain_register is very tricky. It implies once
the same nb is added,
new added nb->next and old one's existing in the chain are changed at
the same time. It is
very dangerous because the whole linked list are corrupted. If we still
keep current logic
to make it simple and beautiful, I hope we should add some comments on
the function at least.