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| author | Loic Prylli <loic@myri.com> | 2007-07-06 13:39:52 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-06 21:23:43 +0400 |
| commit | d25c1ba2fa1a9a1a4f68bef8edb0efefd79f0012 (patch) | |
| tree | 105a72189d2783bfbca1ffda4f5ebf968ac69496 | |
| parent | 1e2e99f0e4aa6363e8515ed17011c210c8f1b52a (diff) | |
| download | linux-d25c1ba2fa1a9a1a4f68bef8edb0efefd79f0012.tar.xz | |
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 <loic@myri.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | 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 55b005152a11..75dc6d5214bc 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); /* |