From 5f40b909728ad784eb43aa309d3c4e9bdf050781 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 19 Oct 2012 17:53:01 +0100 Subject: ARM: 7559/1: smp: switch away from the idmap before updating init_mm.mm_count When booting a secondary CPU, the primary CPU hands two sets of page tables via the secondary_data struct: (1) swapper_pg_dir: a normal, cacheable, shared (if SMP) mapping of the kernel image (i.e. the tables used by init_mm). (2) idmap_pgd: an uncached mapping of the .idmap.text ELF section. The idmap is generally used when enabling and disabling the MMU, which includes early CPU boot. In this case, the secondary CPU switches to swapper as soon as it enters C code: struct mm_struct *mm = &init_mm; unsigned int cpu = smp_processor_id(); /* * All kernel threads share the same mm context; grab a * reference and switch to it. */ atomic_inc(&mm->mm_count); current->active_mm = mm; cpumask_set_cpu(cpu, mm_cpumask(mm)); cpu_switch_mm(mm->pgd, mm); This causes a problem on ARMv7, where the identity mapping is treated as strongly-ordered leading to architecturally UNPREDICTABLE behaviour of exclusive accesses, such as those used by atomic_inc. This patch re-orders the secondary_start_kernel function so that we switch to swapper before performing any exclusive accesses. Cc: Cc: David McKay Reported-by: Gilles Chanteperdrix Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/kernel/smp.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) (limited to 'arch/arm/kernel/smp.c') diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 8e20754dd31d..fbc8b2623d82 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -294,18 +294,24 @@ static void percpu_timer_setup(void); asmlinkage void __cpuinit secondary_start_kernel(void) { struct mm_struct *mm = &init_mm; - unsigned int cpu = smp_processor_id(); + unsigned int cpu; + + /* + * The identity mapping is uncached (strongly ordered), so + * switch away from it before attempting any exclusive accesses. + */ + cpu_switch_mm(mm->pgd, mm); + enter_lazy_tlb(mm, current); + local_flush_tlb_all(); /* * All kernel threads share the same mm context; grab a * reference and switch to it. */ + cpu = smp_processor_id(); atomic_inc(&mm->mm_count); current->active_mm = mm; cpumask_set_cpu(cpu, mm_cpumask(mm)); - cpu_switch_mm(mm->pgd, mm); - enter_lazy_tlb(mm, current); - local_flush_tlb_all(); printk("CPU%u: Booted secondary processor\n", cpu); -- cgit v1.2.3 From b62655f4c6f3e4d21934eee14ac2ac5cd479c97c Mon Sep 17 00:00:00 2001 From: Shawn Guo Date: Tue, 6 Nov 2012 03:48:40 +0100 Subject: ARM: 7571/1: SMP: add function arch_send_wakeup_ipi_mask() Add function arch_send_wakeup_ipi_mask(), so that platform code can use it as an easy way to wake up cores that are in WFI. Signed-off-by: Shawn Guo Signed-off-by: Russell King --- arch/arm/include/asm/smp.h | 1 + arch/arm/kernel/smp.c | 5 +++++ 2 files changed, 6 insertions(+) (limited to 'arch/arm/kernel/smp.c') diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h index 2e3be16c6766..d3a22bebe6ce 100644 --- a/arch/arm/include/asm/smp.h +++ b/arch/arm/include/asm/smp.h @@ -79,6 +79,7 @@ extern void cpu_die(void); extern void arch_send_call_function_single_ipi(int cpu); extern void arch_send_call_function_ipi_mask(const struct cpumask *mask); +extern void arch_send_wakeup_ipi_mask(const struct cpumask *mask); struct smp_operations { #ifdef CONFIG_SMP diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 8e20754dd31d..dd5dd0248b88 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -415,6 +415,11 @@ void arch_send_call_function_ipi_mask(const struct cpumask *mask) smp_cross_call(mask, IPI_CALL_FUNC); } +void arch_send_wakeup_ipi_mask(const struct cpumask *mask) +{ + smp_cross_call(mask, IPI_WAKEUP); +} + void arch_send_call_function_single_ipi(int cpu) { smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE); -- cgit v1.2.3 From 026b7c6bf0bf044aa03e2affbda73b6c6a302538 Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Mon, 3 Dec 2012 21:13:03 +0100 Subject: ARM: 7590/1: /proc/interrupts: limit the display of IPIs to online CPUs only This is what is done for the regular interrupts in kernel/irqs/proc.c already, before calling arch_show_interrupts(). Not doing so for the IPIs causes the column headers not to match with the content whenever some CPUs are offline. Signed-off-by: Nicolas Pitre Signed-off-by: Russell King --- arch/arm/kernel/smp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/arm/kernel/smp.c') diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index fbc8b2623d82..fc4d526e2906 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -443,7 +443,7 @@ void show_ipi_list(struct seq_file *p, int prec) for (i = 0; i < NR_IPI; i++) { seq_printf(p, "%*s%u: ", prec - 1, "IPI", i); - for_each_present_cpu(cpu) + for_each_online_cpu(cpu) seq_printf(p, "%10u ", __get_irq_stat(cpu, ipi_irqs[i])); -- cgit v1.2.3