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Message-ID: <468035BC.9080008@myri.com> Date: Mon, 25 Jun 2007 17:38:04 -0400 From: Loic Prylli <loic@...i.com> To: linux-kernel@...r.kernel.org Subject: [PATCH] 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@...i.com> --- 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); /* -- 1.5.2.2 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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