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Commit 53595345 authored by Tony Luck's avatar Tony Luck Committed by Borislav Petkov
Browse files

EDAC, i7core: 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 i7core_mce_check_error() is called.

Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
Acked-by: default avatarMauro Carvalho Chehab <mchehab@osg.samsung.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/29ab2c370915c6e132fc5d88e7b72cb834bedbfe.1461855008.git.tony.luck@intel.com


Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
parent de0336b3

drivers/edac/i7core_edac.c

+5 −76
Original line number Diff line number Diff line
@@ -271,16 +271,6 @@ struct i7core_pvt { 


	bool		is_registered, enable_scrub;



	/* 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;



	/* DCLK Frequency used for computing scrub rate */

	int			dclk_freq;
@@ -1792,56 +1782,15 @@ static void i7core_mce_output_error(struct mem_ctl_info *mci, 
 *	i7core_check_error	Retrieve and process errors reported by the

 *				hardware. Called by the Core module.

 */

static void i7core_check_error(struct mem_ctl_info *mci)

static void i7core_check_error(struct mem_ctl_info *mci, struct mce *m)

{

	struct i7core_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

	 * losing an error.

	 */

	smp_rmb();

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

		% MCE_LOG_LEN;

	if (!count)

		goto check_ce_error;



	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) {

		i7core_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++)

		i7core_mce_output_error(mci, &pvt->mce_outentry[i]);

	i7core_mce_output_error(mci, m);



	/*

	 * Now, let's increment CE error counts

	 */

check_ce_error:

	if (!pvt->is_registered)

		i7core_udimm_check_mc_ecc_err(mci);

	else
@@ -1849,12 +1798,8 @@ static void i7core_check_error(struct mem_ctl_info *mci) 
}



/*

 * i7core_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 i7core_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.

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

 * of error for us to handle.

 */

static int i7core_mce_check_error(struct notifier_block *nb, unsigned long val,

				  void *data)
@@ -1882,21 +1827,7 @@ static int i7core_mce_check_error(struct notifier_block *nb, unsigned long val, 
	if (mce->bank != 8)

		return NOTIFY_DONE;



	smp_rmb();

	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)

		i7core_check_error(mci);

	i7core_check_error(mci, mce);



	/* Advise mcelog that the errors were handled */

	return NOTIFY_STOP;
@@ -2243,8 +2174,6 @@ static int i7core_register_mci(struct i7core_dev *i7core_dev) 
	get_dimm_config(mci);

	/* record ptr to the generic device */

	mci->pdev = &i7core_dev->pdev[0]->dev;

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

	mci->edac_check = i7core_check_error;



	/* Enable scrubrate setting */

	if (pvt->enable_scrub)