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

  f29a7aff4bd60 ("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: Tony Luck <tony.luck@intel.com>
Acked-by: Mauro 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: Borislav Petkov <bp@suse.de>

diff --git a/drivers/edac/i7core_edac.c b/drivers/edac/i7core_edac.c
index 01087a38da226d08bd7e08da5a183885fbf420b1..60e0bb53e9c9eccc0364148e673b7444a46384a9 100644 (file)
--- a/drivers/edac/i7core_edac.c
+++ b/drivers/edac/i7core_edac.c
@@ -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 @@ check_ce_error:
 }
 
 /*
- * 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)