percpu-refcount: init ->confirm_switch member properly
This patch targets two things which are related to ->confirm_switch: 1. Init ->confirm_switch pointer with NULL on percpu_ref_init() or kernel frightfully complains with WARN_ON_ONCE(ref->confirm_switch) at __percpu_ref_switch_to_atomic if memory chunk was not properly zeroed. 2. Warn if RCU callback is still in progress on percpu_ref_exit(). The race still exists, because percpu_ref_call_confirm_rcu() drops ->confirm_switch to NULL early, but that is only a warning and still the caller is responsible that ref is no longer in active use. Hopefully that can help to catch incorrect usage of percpu-refcount. Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com> Cc: Tejun Heo <tj@kernel.org> Cc: linux-kernel@vger.kernel.org Signed-off-by: Tejun Heo <tj@kernel.org>
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