Commit:     d25c1ba2fa1a9a1a4f68bef8edb0efefd79f0012
Parent:     1e2e99f0e4aa6363e8515ed17011c210c8f1b52a
Author:     Loic Prylli <[EMAIL PROTECTED]>
AuthorDate: Fri Jul 6 02:39:52 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Fri Jul 6 10:23:43 2007 -0700

    MTRR: Fix race causing set_mtrr to go into infinite loop
    Processors synchronization in set_mtrr requires the .gate field to be set
    after .count field is properly initialized.  Without an explicit barrier,
    the compiler was reordering those memory stores.  That was sometimes
    causing a processor (in ipi_handler) to see the .gate change and decrement
    .count before the latter is set by set_mtrr() (which then hangs in a
    infinite loop with irqs disabled).
    Signed-off-by: Loic Prylli <[EMAIL PROTECTED]>
    Cc: Andi Kleen <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 arch/i386/kernel/cpu/mtrr/main.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/i386/kernel/cpu/mtrr/main.c b/arch/i386/kernel/cpu/mtrr/main.c
index 55b0051..75dc6d5 100644
--- a/arch/i386/kernel/cpu/mtrr/main.c
+++ b/arch/i386/kernel/cpu/mtrr/main.c
@@ -229,6 +229,8 @@ static void set_mtrr(unsigned int reg, unsigned long base,
        data.smp_size = size;
        data.smp_type = type;
        atomic_set(&data.count, num_booting_cpus() - 1);
+       /* make sure data.count is visible before unleashing other CPUs */
+       smp_wmb();
        /*  Start the ball rolling on other CPUs  */
@@ -242,6 +244,7 @@ static void set_mtrr(unsigned int reg, unsigned long base,
        /* ok, reset count and toggle gate */
        atomic_set(&data.count, num_booting_cpus() - 1);
+       smp_wmb();
        /* do our MTRR business */
@@ -260,6 +263,7 @@ static void set_mtrr(unsigned int reg, unsigned long base,
        atomic_set(&data.count, num_booting_cpus() - 1);
+       smp_wmb();
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