drivers/edac: mod race fix i82875p
authorJason Uhlenkott <juhlenko@akamai.com>
Thu, 19 Jul 2007 08:50:16 +0000 (01:50 -0700)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>
Thu, 19 Jul 2007 17:04:55 +0000 (10:04 -0700)
If ERRSTS indicates that there's no error then we don't need to bother reading
the other registers.

In addition to making the common case faster, this actually fixes a small race
where we don't see an error but we clear the error bits anyway, potentially
wiping away info on an error that happened in the interim (or where a CE
arrives between the first and second read of ERRSTS, causing us to falsely
claim "UE overwrote CE").

Signed-off-by: Jason Uhlenkott <juhlenko@akamai.com>
Signed-off-by: Douglas Thompson <dougthompson@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/edac/i82875p_edac.c

index c9aed70fec8eab98ba03bf626cc713018cb9183a..089ec397ca6a610751a1c70b01efaa708dfc7f74 100644 (file)
@@ -198,27 +198,28 @@ static void i82875p_get_error_info(struct mem_ctl_info *mci,
         * overwritten by UE.
         */
        pci_read_config_word(pdev, I82875P_ERRSTS, &info->errsts);
+
+       if (!(info->errsts & 0x0081))
+               return;
+
        pci_read_config_dword(pdev, I82875P_EAP, &info->eap);
        pci_read_config_byte(pdev, I82875P_DES, &info->des);
        pci_read_config_byte(pdev, I82875P_DERRSYN, &info->derrsyn);
        pci_read_config_word(pdev, I82875P_ERRSTS, &info->errsts2);
 
-       pci_write_bits16(pdev, I82875P_ERRSTS, 0x0081, 0x0081);
-
        /*
         * If the error is the same then we can for both reads then
         * the first set of reads is valid.  If there is a change then
         * there is a CE no info and the second set of reads is valid
         * and should be UE info.
         */
-       if (!(info->errsts2 & 0x0081))
-               return;
-
        if ((info->errsts ^ info->errsts2) & 0x0081) {
                pci_read_config_dword(pdev, I82875P_EAP, &info->eap);
                pci_read_config_byte(pdev, I82875P_DES, &info->des);
                pci_read_config_byte(pdev, I82875P_DERRSYN, &info->derrsyn);
        }
+
+       pci_write_bits16(pdev, I82875P_ERRSTS, 0x0081, 0x0081);
 }
 
 static int i82875p_process_error_info(struct mem_ctl_info *mci,
@@ -229,7 +230,7 @@ static int i82875p_process_error_info(struct mem_ctl_info *mci,
 
        multi_chan = mci->csrows[0].nr_channels - 1;
 
-       if (!(info->errsts2 & 0x0081))
+       if (!(info->errsts & 0x0081))
                return 0;
 
        if (!handle_errors)