summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorCatalin Marinas <catalin.marinas@arm.com>2010-01-26 19:09:42 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2010-02-15 21:39:51 +0000
commit11805bcfa411c816b7c76fc40724be6733c74ffc (patch)
tree09c5c6c91deffb60339f027779521bafa42921ce
parent48ab7e09e0a7c00a217f87e4b57dfbee9c603e79 (diff)
ARM: 5905/1: ARM: Global ASID allocation on SMP
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>
-rw-r--r--arch/arm/include/asm/mmu.h1
-rw-r--r--arch/arm/include/asm/mmu_context.h15
-rw-r--r--arch/arm/mm/context.c124
3 files changed, 126 insertions, 14 deletions
diff --git a/arch/arm/include/asm/mmu.h b/arch/arm/include/asm/mmu.h
index b561584d04a1..68870c776671 100644
--- a/arch/arm/include/asm/mmu.h
+++ b/arch/arm/include/asm/mmu.h
@@ -6,6 +6,7 @@
typedef struct {
#ifdef CONFIG_CPU_HAS_ASID
unsigned int id;
+ spinlock_t id_lock;
#endif
unsigned int kvm_seq;
} mm_context_t;
diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h
index de6cefb329dd..a0b3cac0547c 100644
--- a/arch/arm/include/asm/mmu_context.h
+++ b/arch/arm/include/asm/mmu_context.h
@@ -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())
diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c
index a9e22e31eaa1..b0ee9ba3cfab 100644
--- a/arch/arm/mm/context.c
+++ b/arch/arm/mm/context.c
@@ -10,12 +10,17 @@
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/percpu.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
static DEFINE_SPINLOCK(cpu_asid_lock);
unsigned int cpu_last_asid = ASID_FIRST_VERSION;
+#ifdef CONFIG_SMP
+DEFINE_PER_CPU(struct mm_struct *, current_mm);
+#endif
/*
* We fork()ed a process, and we need a new context for the child
@@ -26,13 +31,109 @@ unsigned int cpu_last_asid = ASID_FIRST_VERSION;
void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
mm->context.id = 0;
+ spin_lock_init(&mm->context.id_lock);
}
+static void flush_context(void)
+{
+ /* set the reserved ASID before flushing the TLB */
+ asm("mcr p15, 0, %0, c13, c0, 1\n" : : "r" (0));
+ isb();
+ local_flush_tlb_all();
+ if (icache_is_vivt_asid_tagged()) {
+ __flush_icache_all();
+ dsb();
+ }
+}
+
+#ifdef CONFIG_SMP
+
+static void set_mm_context(struct mm_struct *mm, unsigned int asid)
+{
+ unsigned long flags;
+
+ /*
+ * Locking needed for multi-threaded applications where the
+ * same mm->context.id could be set from different CPUs during
+ * the broadcast. This function is also called via IPI so the
+ * mm->context.id_lock has to be IRQ-safe.
+ */
+ spin_lock_irqsave(&mm->context.id_lock, flags);
+ if (likely((mm->context.id ^ cpu_last_asid) >> ASID_BITS)) {
+ /*
+ * Old version of ASID found. Set the new one and
+ * reset mm_cpumask(mm).
+ */
+ mm->context.id = asid;
+ cpumask_clear(mm_cpumask(mm));
+ }
+ spin_unlock_irqrestore(&mm->context.id_lock, flags);
+
+ /*
+ * Set the mm_cpumask(mm) bit for the current CPU.
+ */
+ cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
+}
+
+/*
+ * Reset the ASID on the current CPU. This function call is broadcast
+ * from the CPU handling the ASID rollover and holding cpu_asid_lock.
+ */
+static void reset_context(void *info)
+{
+ unsigned int asid;
+ unsigned int cpu = smp_processor_id();
+ struct mm_struct *mm = per_cpu(current_mm, cpu);
+
+ /*
+ * Check if a current_mm was set on this CPU as it might still
+ * be in the early booting stages and using the reserved ASID.
+ */
+ if (!mm)
+ return;
+
+ smp_rmb();
+ asid = cpu_last_asid + cpu + 1;
+
+ flush_context();
+ set_mm_context(mm, asid);
+
+ /* set the new ASID */
+ asm("mcr p15, 0, %0, c13, c0, 1\n" : : "r" (mm->context.id));
+ isb();
+}
+
+#else
+
+static inline void set_mm_context(struct mm_struct *mm, unsigned int asid)
+{
+ mm->context.id = asid;
+ cpumask_copy(mm_cpumask(mm), cpumask_of(smp_processor_id()));
+}
+
+#endif
+
void __new_context(struct mm_struct *mm)
{
unsigned int asid;
spin_lock(&cpu_asid_lock);
+#ifdef CONFIG_SMP
+ /*
+ * Check the ASID again, in case the change was broadcast from
+ * another CPU before we acquired the lock.
+ */
+ if (unlikely(((mm->context.id ^ cpu_last_asid) >> ASID_BITS) == 0)) {
+ cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
+ spin_unlock(&cpu_asid_lock);
+ return;
+ }
+#endif
+ /*
+ * At this point, it is guaranteed that the current mm (with
+ * an old ASID) isn't active on any other CPU since the ASIDs
+ * are changed simultaneously via IPI.
+ */
asid = ++cpu_last_asid;
if (asid == 0)
asid = cpu_last_asid = ASID_FIRST_VERSION;
@@ -42,20 +143,15 @@ void __new_context(struct mm_struct *mm)
* to start a new version and flush the TLB.
*/
if (unlikely((asid & ~ASID_MASK) == 0)) {
- asid = ++cpu_last_asid;
- /* set the reserved ASID before flushing the TLB */
- asm("mcr p15, 0, %0, c13, c0, 1 @ set reserved context ID\n"
- :
- : "r" (0));
- isb();
- flush_tlb_all();
- if (icache_is_vivt_asid_tagged()) {
- __flush_icache_all();
- dsb();
- }
+ asid = cpu_last_asid + smp_processor_id() + 1;
+ flush_context();
+#ifdef CONFIG_SMP
+ smp_wmb();
+ smp_call_function(reset_context, NULL, 1);
+#endif
+ cpu_last_asid += NR_CPUS;
}
- spin_unlock(&cpu_asid_lock);
- cpumask_copy(mm_cpumask(mm), cpumask_of(smp_processor_id()));
- mm->context.id = asid;
+ set_mm_context(mm, asid);
+ spin_unlock(&cpu_asid_lock);
}