The patch titled
MTRR: Fix race causing set_mtrr to go into infinite loop
has been added to the -mm tree. Its filename is
mtrr-fix-race-causing-set_mtrr-to-go-into-infinite-loop.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: MTRR: Fix race causing set_mtrr to go into infinite loop
From: Loic Prylli <loic@xxxxxxxx>
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 <loic@xxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/i386/kernel/cpu/mtrr/main.c | 4 ++++
1 file changed, 4 insertions(+)
diff -puN arch/i386/kernel/cpu/mtrr/main.c~mtrr-fix-race-causing-set_mtrr-to-go-into-infinite-loop arch/i386/kernel/cpu/mtrr/main.c
--- a/arch/i386/kernel/cpu/mtrr/main.c~mtrr-fix-race-causing-set_mtrr-to-go-into-infinite-loop
+++ a/arch/i386/kernel/cpu/mtrr/main.c
@@ -229,6 +229,8 @@ static void set_mtrr(unsigned int reg, u
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, u
/* 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, u
cpu_relax();
atomic_set(&data.count, num_booting_cpus() - 1);
+ smp_wmb();
atomic_set(&data.gate,0);
/*
_
Patches currently in -mm which might be from loic@xxxxxxxx are
mtrr-fix-race-causing-set_mtrr-to-go-into-infinite-loop.patch
-
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