Messages in this thread Patch in this message | | | Subject | Re: smp.c && barriers (Was: [PATCH 1/4] generic-smp: remove single ipi fallback for smp_call_function_many()) | From | Suresh Siddha <> | Date | Thu, 19 Feb 2009 14:00:24 -0800 |
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On Thu, 2009-02-19 at 04:20 -0800, Ingo Molnar wrote: > Could you please refresh this patch to latest tip:master? The > APIC drivers moved to arch/x86/kernel/apic/.
Appended the refreshed patch. Thanks. ---
From: Suresh Siddha <suresh.b.siddha@intel.com> Subject: x86: move smp_mb() in flush tlb path to x2apic specific paths
uncached MMIO accesses for xapic are inherently serializing and hence we don't need explicit barriers for xapic IPI paths.
x2apic MSR writes/reads don't have serializing semantics and hence need a serializing instruction or mfence, to make all the previous memory stores globally visisble before the x2apic msr write for IPI.
And hence move smp_mb() in x86 flush tlb path to x2apic specific paths.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> ---
diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c index 3f7df23..c54fffe 100644 --- a/arch/x86/kernel/apic/x2apic_cluster.c +++ b/arch/x86/kernel/apic/x2apic_cluster.c @@ -63,6 +63,13 @@ static void x2apic_send_IPI_mask(const struct cpumask *mask, int vector) unsigned long query_cpu; unsigned long flags; + /* + * Make previous memory operations globally visible before + * sending the IPI. We need a serializing instruction or mfence + * for this. + */ + smp_mb(); + local_irq_save(flags); for_each_cpu(query_cpu, mask) { __x2apic_send_IPI_dest( @@ -79,6 +86,13 @@ static void unsigned long query_cpu; unsigned long flags; + /* + * Make previous memory operations globally visible before + * sending the IPI. We need a serializing instruction or mfence + * for this. + */ + smp_mb(); + local_irq_save(flags); for_each_cpu(query_cpu, mask) { if (query_cpu == this_cpu) @@ -96,6 +110,13 @@ static void x2apic_send_IPI_allbutself(int vector) unsigned long query_cpu; unsigned long flags; + /* + * Make previous memory operations globally visible before + * sending the IPI. We need a serializing instruction or mfence + * for this. + */ + smp_mb(); + local_irq_save(flags); for_each_online_cpu(query_cpu) { if (query_cpu == this_cpu) diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c index d2d52eb..84cc2f3 100644 --- a/arch/x86/kernel/apic/x2apic_phys.c +++ b/arch/x86/kernel/apic/x2apic_phys.c @@ -58,6 +58,13 @@ static void x2apic_send_IPI_mask(const struct cpumask *mask, int vector) unsigned long query_cpu; unsigned long flags; + /* + * Make previous memory operations globally visible before + * sending the IPI. We need a serializing instruction or mfence + * for this. + */ + smp_mb(); + local_irq_save(flags); for_each_cpu(query_cpu, mask) { __x2apic_send_IPI_dest(per_cpu(x86_cpu_to_apicid, query_cpu), @@ -73,6 +80,13 @@ static void unsigned long query_cpu; unsigned long flags; + /* + * Make previous memory operations globally visible before + * sending the IPI. We need a serializing instruction or mfence + * for this. + */ + smp_mb(); + local_irq_save(flags); for_each_cpu(query_cpu, mask) { if (query_cpu != this_cpu) @@ -89,6 +103,13 @@ static void x2apic_send_IPI_allbutself(int vector) unsigned long query_cpu; unsigned long flags; + /* + * Make previous memory operations globally visible before + * sending the IPI. We need a serializing instruction or mfence + * for this. + */ + smp_mb(); + local_irq_save(flags); for_each_online_cpu(query_cpu) { if (query_cpu == this_cpu) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index a654d59..821e970 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -187,11 +187,6 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask, cpumask, cpumask_of(smp_processor_id())); /* - * Make the above memory operations globally visible before - * sending the IPI. - */ - smp_mb(); - /* * We have to send the IPI only to * CPUs affected. */
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