Commit:     4f84e4be53a04a65d97bf0faa0c8f99e29bc0170
Parent:     d8aaf12142d066d3982475d58a9094c85a06a5a9
Author:     Joshua Wise <[EMAIL PROTECTED]>
AuthorDate: Sat Jun 23 17:16:45 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Sun Jun 24 08:59:12 2007 -0700

    x86_64: fix misplaced `continue' in mce.c
      When a userspace application wants to know about machine check events, it
      opens /dev/mcelog and does a read(). Usually, we found that this interface
      works well, but in some cases, when the system was taking large numbers of
      machine check exceptions, the read() would hang. The system would output a
      soft-lockup warning, and the daemon reading from /dev/mcelog would suck up
      as much of a single CPU as it could spinning in system space.
      This patch fixes this bug. In particular, there was a "continue" inside a
      timeout loop that presumably was intended to break out of the outer loop,
      but instead caused the inner loop to continue. This patch also makes the
      condition for the break-out a little more evident by changing a
      !time_before to a time_after_eq.
      The read() no longer hangs in this test case.
      On my system, I could replicate the bug with the following command:
        # for i in `seq 15000`; do ./; done
      where contains commands to inject a single-bit error into 
      next memory write transaction.
      This patch is against git f1518a088bde6aea49e7c472ed6ab96178fcba3e.
    Signed-off-by: Joshua Wise <[EMAIL PROTECTED]>
    Signed-off-by: Tim Hockin <[EMAIL PROTECTED]>
    Cc: Andi Kleen <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 arch/x86_64/kernel/mce.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86_64/kernel/mce.c b/arch/x86_64/kernel/mce.c
index a14375d..aa1d159 100644
--- a/arch/x86_64/kernel/mce.c
+++ b/arch/x86_64/kernel/mce.c
@@ -497,15 +497,17 @@ static ssize_t mce_read(struct file *filp, char __user 
*ubuf, size_t usize, loff
        for (i = 0; i < next; i++) {            
                unsigned long start = jiffies;
                while (!mcelog.entry[i].finished) {
-                       if (!time_before(jiffies, start + 2)) {
+                       if (time_after_eq(jiffies, start + 2)) {
                                memset(mcelog.entry + i,0, sizeof(struct mce));
-                               continue;
+                               goto timeout;
                err |= copy_to_user(buf, mcelog.entry + i, sizeof(struct mce));
                buf += sizeof(struct mce); 
+ timeout:
+               ;
        memset(mcelog.entry, 0, next * sizeof(struct mce));
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