@@ -835,6 +835,8 @@ do { \
{ .notifier_call = fn, .priority = CPU_PRI_PERF }; \
unsigned long cpu = smp_processor_id(); \
unsigned long flags; \
+ \
+ cpu_notifier_register_begin(); \
fn(&fn##_nb, (unsigned long)CPU_UP_PREPARE, \
(void *)(unsigned long)cpu); \
local_irq_save(flags); \
@@ -843,9 +845,21 @@ do { \
local_irq_restore(flags); \
fn(&fn##_nb, (unsigned long)CPU_ONLINE, \
(void *)(unsigned long)cpu); \
- register_cpu_notifier(&fn##_nb); \
+ __register_cpu_notifier(&fn##_nb); \
+ cpu_notifier_register_done(); \
} while (0)
+/*
+ * Bare-bones version of perf_cpu_notifier(), which doesn't invoke the
+ * callback for already online CPUs.
+ */
+#define __perf_cpu_notifier(fn) \
+do { \
+ static struct notifier_block fn##_nb = \
+ { .notifier_call = fn, .priority = CPU_PRI_PERF }; \
+ \
+ __register_cpu_notifier(&fn##_nb); \
+} while (0)
struct perf_pmu_events_attr {
struct device_attribute attr;
Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the perf subsystem's hotplug notifier by using this latter form of callback registration. Also provide a bare-bones version of perf_cpu_notifier() that doesn't invoke the notifiers for the already online CPUs. This would be useful for subsystems that need to perform a different set of initialization for the already online CPUs, or don't need the initialization altogether. Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> --- include/linux/perf_event.h | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html