arm: perf: fold hotplug notifier into arm_pmu

Handling multiple PMUs using a single hotplug notifier requires a list
of PMUs to be maintained, with synchronisation in the probe, remove, and
notify paths. This is error-prone and makes the code much harder to
maintain.

Instead of using a single notifier, we can dynamically allocate a
notifier block per-PMU. The end result is the same, but the list of PMUs
is implicit in the hotplug notifier list rather than within a perf-local
data structure, which makes the code far easier to handle.

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/arm/include/asm/pmu.h b/arch/arm/include/asm/pmu.h
index cc014983550..b1596bd5912 100644
--- a/arch/arm/include/asm/pmu.h
+++ b/arch/arm/include/asm/pmu.h
@@ -116,6 +116,7 @@ struct arm_pmu {
 	u64		max_period;
 	struct platform_device	*plat_device;
 	struct pmu_hw_events	__percpu *hw_events;
+	struct notifier_block	hotplug_nb;
 };
 
 #define to_arm_pmu(p) (container_of(p, struct arm_pmu, pmu))