Messages in this thread Patch in this message | | | Date | Mon, 6 Jun 2011 16:57:08 +0200 | From | Stephane Eranian <> | Subject | [PATCH 2/3] perf_events: fix validation of events using an extra reg (v4) |
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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.
The fourth version fixes a compilation problem when Intel processors are not supported (CONFIG_CPU_SUP_INTEL). Thanks to Peter Zijsltra for reporting the bug and suggesting the fix.
Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Stephane Eranian <eranian@google.com> --
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index 0f8d3ff..ed6af75 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -1682,6 +1682,40 @@ 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 = 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 @@ -1692,9 +1726,9 @@ 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); @@ -1704,7 +1738,7 @@ 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; } @@ -1724,35 +1758,32 @@ 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; } diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c index 2d40f33..69afaad 100644 --- a/arch/x86/kernel/cpu/perf_event_intel.c +++ b/arch/x86/kernel/cpu/perf_event_intel.c @@ -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 */
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