Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d25c1ba2fa1a9a1a4f68bef8edb0efefd79f0012
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();
atomic_set(&data.gate,0);
/* 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();
atomic_set(&data.gate,1);
/* do our MTRR business */
@@ -260,6 +263,7 @@ static void set_mtrr(unsigned int reg, unsigned long base,
cpu_relax();
atomic_set(&data.count, num_booting_cpus() - 1);
+ smp_wmb();
atomic_set(&data.gate,0);
/*
-
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