perf_events: Fix validation of events using an extra reg
Stephane Eranian [Mon, 6 Jun 2011 14:57:08 +0000 (16:57 +0200)]
The validate_group() function needs to validate events with
extra shared regs. Within an event group, only events with
the same value for the extra reg can co-exist. This was not
checked by validate_group() because it was missing the
shared_regs logic.

This patch changes the allocation of the fake cpuc used for
validation to also point to a fake shared_regs structure such
that group events be properly testing.

It modifies __intel_shared_reg_get_constraints() to use
spin_lock_irqsave() to avoid lockdep issues.

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110606145708.GA7279@quad
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/perf_event.c
arch/x86/kernel/cpu/perf_event_intel.c

index 019fda7..9a0f55c 100644 (file)
@@ -1689,6 +1689,40 @@ static int x86_pmu_commit_txn(struct pmu *pmu)
        perf_pmu_enable(pmu);
        return 0;
 }
+/*
+ * a fake_cpuc is used to validate event groups. Due to
+ * the extra reg logic, we need to also allocate a fake
+ * per_core and per_cpu structure. Otherwise, group events
+ * using extra reg may conflict without the kernel being
+ * able to catch this when the last event gets added to
+ * the group.
+ */
+static void free_fake_cpuc(struct cpu_hw_events *cpuc)
+{
+       kfree(cpuc->shared_regs);
+       kfree(cpuc);
+}
+
+static struct cpu_hw_events *allocate_fake_cpuc(void)
+{
+       struct cpu_hw_events *cpuc;
+       int cpu = raw_smp_processor_id();
+
+       cpuc = kzalloc(sizeof(*cpuc), GFP_KERNEL);
+       if (!cpuc)
+               return ERR_PTR(-ENOMEM);
+
+       /* only needed, if we have extra_regs */
+       if (x86_pmu.extra_regs) {
+               cpuc->shared_regs = allocate_shared_regs(cpu);
+               if (!cpuc->shared_regs)
+                       goto error;
+       }
+       return cpuc;
+error:
+       free_fake_cpuc(cpuc);
+       return ERR_PTR(-ENOMEM);
+}
 
 /*
  * validate that we can schedule this event
@@ -1699,9 +1733,9 @@ static int validate_event(struct perf_event *event)
        struct event_constraint *c;
        int ret = 0;
 
-       fake_cpuc = kmalloc(sizeof(*fake_cpuc), GFP_KERNEL | __GFP_ZERO);
-       if (!fake_cpuc)
-               return -ENOMEM;
+       fake_cpuc = allocate_fake_cpuc();
+       if (IS_ERR(fake_cpuc))
+               return PTR_ERR(fake_cpuc);
 
        c = x86_pmu.get_event_constraints(fake_cpuc, event);
 
@@ -1711,7 +1745,7 @@ static int validate_event(struct perf_event *event)
        if (x86_pmu.put_event_constraints)
                x86_pmu.put_event_constraints(fake_cpuc, event);
 
-       kfree(fake_cpuc);
+       free_fake_cpuc(fake_cpuc);
 
        return ret;
 }
@@ -1731,35 +1765,32 @@ static int validate_group(struct perf_event *event)
 {
        struct perf_event *leader = event->group_leader;
        struct cpu_hw_events *fake_cpuc;
-       int ret, n;
+       int ret = -ENOSPC, n;
 
-       ret = -ENOMEM;
-       fake_cpuc = kmalloc(sizeof(*fake_cpuc), GFP_KERNEL | __GFP_ZERO);
-       if (!fake_cpuc)
-               goto out;
+       fake_cpuc = allocate_fake_cpuc();
+       if (IS_ERR(fake_cpuc))
+               return PTR_ERR(fake_cpuc);
        /*
         * the event is not yet connected with its
         * siblings therefore we must first collect
         * existing siblings, then add the new event
         * before we can simulate the scheduling
         */
-       ret = -ENOSPC;
        n = collect_events(fake_cpuc, leader, true);
        if (n < 0)
-               goto out_free;
+               goto out;
 
        fake_cpuc->n_events = n;
        n = collect_events(fake_cpuc, event, false);
        if (n < 0)
-               goto out_free;
+               goto out;
 
        fake_cpuc->n_events = n;
 
        ret = x86_pmu.schedule_events(fake_cpuc, n, NULL);
 
-out_free:
-       kfree(fake_cpuc);
 out:
+       free_fake_cpuc(fake_cpuc);
        return ret;
 }
 
index 6ad95ba..ac02b83 100644 (file)
@@ -1027,14 +1027,18 @@ __intel_shared_reg_get_constraints(struct cpu_hw_events *cpuc,
 {
        struct event_constraint *c = &emptyconstraint;
        struct er_account *era;
+       unsigned long flags;
 
        /* already allocated shared msr */
-       if (reg->alloc || !cpuc->shared_regs)
+       if (reg->alloc)
                return &unconstrained;
 
        era = &cpuc->shared_regs->regs[reg->idx];
-
-       raw_spin_lock(&era->lock);
+       /*
+        * we use spin_lock_irqsave() to avoid lockdep issues when
+        * passing a fake cpuc
+        */
+       raw_spin_lock_irqsave(&era->lock, flags);
 
        if (!atomic_read(&era->ref) || era->config == reg->config) {
 
@@ -1058,7 +1062,7 @@ __intel_shared_reg_get_constraints(struct cpu_hw_events *cpuc,
                 */
                c = &unconstrained;
        }
-       raw_spin_unlock(&era->lock);
+       raw_spin_unlock_irqrestore(&era->lock, flags);
 
        return c;
 }
@@ -1524,4 +1528,8 @@ static int intel_pmu_init(void)
        return 0;
 }
 
+static struct intel_shared_regs *allocate_shared_regs(int cpu)
+{
+       return NULL;
+}
 #endif /* CONFIG_CPU_SUP_INTEL */