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ARM: 5905/1: ARM: Global ASID allocation on SMP

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The current ASID allocation algorithm doesn't ensure the notification
of the other CPUs when the ASID rolls over. This may lead to two
processes using the same ASID (but different generation) or multiple
threads of the same process using different ASIDs.

This patch adds the broadcasting of the ASID rollover event to the
other CPUs. To avoid a race on multiple CPUs modifying "cpu_last_asid"
during the handling of the broadcast, the ASID numbering now starts at
"smp_processor_id() + 1". At rollover, the cpu_last_asid will be set
to NR_CPUS.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Catalin Marinas
2010-01-26 19:09:42 +01:00
committed by Russell King
parent 48ab7e09e0
commit 11805bcfa4
3 changed files with 126 additions and 14 deletions
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15
arch/arm/include/asm/mmu_context.h
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@@ -43,12 +43,23 @@ void __check_kvm_seq(struct mm_struct *mm);
#define ASID_FIRST_VERSION (1 << ASID_BITS)
extern unsigned int cpu_last_asid;
#ifdef CONFIG_SMP
DECLARE_PER_CPU(struct mm_struct *, current_mm);
#endif
void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
void __new_context(struct mm_struct *mm);
static inline void check_context(struct mm_struct *mm)
{
/*
* This code is executed with interrupts enabled. Therefore,
* mm->context.id cannot be updated to the latest ASID version
* on a different CPU (and condition below not triggered)
* without first getting an IPI to reset the context. The
* alternative is to take a read_lock on mm->context.id_lock
* (after changing its type to rwlock_t).
*/
if (unlikely((mm->context.id ^ cpu_last_asid) >> ASID_BITS))
__new_context(mm);
@@ -108,6 +119,10 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
__flush_icache_all();
#endif
if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next) {
#ifdef CONFIG_SMP
struct mm_struct **crt_mm = &per_cpu(current_mm, cpu);
*crt_mm = next;
#endif
check_context(next);
cpu_switch_mm(next->pgd, next);
if (cache_is_vivt())