Quoting Sai Prakash Ranjan (2020-07-28 22:13:10) > etm4_count keeps track of number of ETMv4 registered and on some systems, > a race is observed on etm4_count variable which can lead to multiple calls > to cpuhp_setup_state_nocalls_cpuslocked(). This function internally calls > cpuhp_store_callbacks() which prevents multiple registrations of callbacks > for a given state and due to this race, it returns -EBUSY leading to ETM > probe failures like below. > > coresight-etm4x: probe of 7040000.etm failed with error -16 > > This race can easily be triggered with async probe by setting probe type > as PROBE_PREFER_ASYNCHRONOUS and with ETM power management property > "arm,coresight-loses-context-with-cpu". > > Prevent this race by moving cpuhp callbacks to etm driver init since the > cpuhp callbacks doesn't have to depend on the etm4_count and can be once > setup during driver init. Similarly we move cpu_pm notifier registration > to driver init and completely remove etm4_count usage. Also now we can > use non cpuslocked version of cpuhp callbacks with this movement. > > Fixes: 9b6a3f3633a5 ("coresight: etmv4: Fix CPU power management setup in > probe() function") > Fixes: 58eb457be028 ("hwtracing/coresight-etm4x: Convert to hotplug state > machine") > Suggested-by: Suzuki K Poulose <suzuki.poul...@arm.com> > Signed-off-by: Sai Prakash Ranjan <saiprakash.ran...@codeaurora.org> > ---
Reviewed-by: Stephen Boyd <swb...@chromium.org> Tested-by: Stephen Boyd <swb...@chromium.org>