Commit ad08c4e9 authored by Tony Luck's avatar Tony Luck Committed by Borislav Petkov
Browse files

EDAC, sb_edac: Remove double buffering of error records 



In the bad old days the functions from x86_mce_decoder_chain could be
called in machine check context. So we used to carefully copy them and
defer processing until later. But in

  f29a7aff ("x86/mce: Avoid potential deadlock due to printk() in MCE context")

we switched the logging code to save the record in a genpool, and call
the functions that registered to be notified later from a work queue.

So drop all the double buffering and do all the work we want to do as
soon as sbridge_mce_check_error() is called.

Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
Cc: Aristeu Rozanski <arozansk@redhat.com>
Cc: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: patrickg@supermicro.com
Link: http://lkml.kernel.org/r/100025611cd780d9bca72792b2b2146760da53e0.1460756761.git.tony.luck@intel.com


Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
parent ab67b6c2

drivers/edac/sb_edac.c

+3 −85
Original line number Original line Diff line number Diff line
@@ -363,16 +363,6 @@ struct sbridge_pvt { 
	/* Memory type detection */

	/* Memory type detection */

	bool			is_mirrored, is_lockstep, is_close_pg;

	bool			is_mirrored, is_lockstep, is_close_pg;





	/* Fifo double buffers */

	struct mce		mce_entry[MCE_LOG_LEN];

	struct mce		mce_outentry[MCE_LOG_LEN];



	/* Fifo in/out counters */

	unsigned		mce_in, mce_out;



	/* Count indicator to show errors not got */

	unsigned		mce_overrun;



	/* Memory description */

	/* Memory description */

	u64			tolm, tohm;

	u64			tolm, tohm;

	struct knl_pvt knl;

	struct knl_pvt knl;
@@ -3075,63 +3065,8 @@ err_parsing: 
}

}





/*

/*

 *	sbridge_check_error	Retrieve and process errors reported by the

 * Check that logging is enabled and that this is the right type

 *				hardware. Called by the Core module.

 * of error for us to handle.

 */

static void sbridge_check_error(struct mem_ctl_info *mci)

{

	struct sbridge_pvt *pvt = mci->pvt_info;

	int i;

	unsigned count = 0;

	struct mce *m;



	/*

	 * MCE first step: Copy all mce errors into a temporary buffer

	 * We use a double buffering here, to reduce the risk of

	 * loosing an error.

	 */

	smp_rmb();

	count = (pvt->mce_out + MCE_LOG_LEN - pvt->mce_in)

		% MCE_LOG_LEN;

	if (!count)

		return;



	m = pvt->mce_outentry;

	if (pvt->mce_in + count > MCE_LOG_LEN) {

		unsigned l = MCE_LOG_LEN - pvt->mce_in;



		memcpy(m, &pvt->mce_entry[pvt->mce_in], sizeof(*m) * l);

		smp_wmb();

		pvt->mce_in = 0;

		count -= l;

		m += l;

	}

	memcpy(m, &pvt->mce_entry[pvt->mce_in], sizeof(*m) * count);

	smp_wmb();

	pvt->mce_in += count;



	smp_rmb();

	if (pvt->mce_overrun) {

		sbridge_printk(KERN_ERR, "Lost %d memory errors\n",

			      pvt->mce_overrun);

		smp_wmb();

		pvt->mce_overrun = 0;

	}



	/*

	 * MCE second step: parse errors and display

	 */

	for (i = 0; i < count; i++)

		sbridge_mce_output_error(mci, &pvt->mce_outentry[i]);

}



/*

 * sbridge_mce_check_error	Replicates mcelog routine to get errors

 *				This routine simply queues mcelog errors, and

 *				return. The error itself should be handled later

 *				by sbridge_check_error.

 * WARNING: As this routine should be called at NMI time, extra care should

 * be taken to avoid deadlocks, and to be as fast as possible.

 */

 */

static int sbridge_mce_check_error(struct notifier_block *nb, unsigned long val,

static int sbridge_mce_check_error(struct notifier_block *nb, unsigned long val,

				   void *data)

				   void *data)
@@ -3176,21 +3111,7 @@ static int sbridge_mce_check_error(struct notifier_block *nb, unsigned long val, 
			  "%u APIC %x\n", mce->cpuvendor, mce->cpuid,

			  "%u APIC %x\n", mce->cpuvendor, mce->cpuid,

			  mce->time, mce->socketid, mce->apicid);

			  mce->time, mce->socketid, mce->apicid);





	smp_rmb();

	sbridge_mce_output_error(mci, mce);

	if ((pvt->mce_out + 1) % MCE_LOG_LEN == pvt->mce_in) {

		smp_wmb();

		pvt->mce_overrun++;

		return NOTIFY_DONE;

	}



	/* Copy memory error at the ringbuffer */

	memcpy(&pvt->mce_entry[pvt->mce_out], mce, sizeof(*mce));

	smp_wmb();

	pvt->mce_out = (pvt->mce_out + 1) % MCE_LOG_LEN;



	/* Handle fatal errors immediately */

	if (mce->mcgstatus & 1)

		sbridge_check_error(mci);





	/* Advice mcelog that the error were handled */

	/* Advice mcelog that the error were handled */

	return NOTIFY_STOP;

	return NOTIFY_STOP;
@@ -3276,9 +3197,6 @@ static int sbridge_register_mci(struct sbridge_dev *sbridge_dev, enum type type) 
	mci->dev_name = pci_name(pdev);

	mci->dev_name = pci_name(pdev);

	mci->ctl_page_to_phys = NULL;

	mci->ctl_page_to_phys = NULL;





	/* Set the function pointer to an actual operation function */

	mci->edac_check = sbridge_check_error;



	pvt->info.type = type;

	pvt->info.type = type;

	switch (type) {

	switch (type) {

	case IVY_BRIDGE:

	case IVY_BRIDGE:

CRA Git | Maintained and supported by SUSTech CRA and CCSE