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The synchronization of CPU offlining with GP initialization is confusing to put it mildly (rightfully so as the issue it deals with is complex). Recent discussions brought up a question -- what prevents the rcu_implicit_dyntick_qs() from warning about QS reports for offline CPUs (missing QS reports for offline CPUs causing indefinite hangs). QS reporting for now-offline CPUs should only happen from: - gp_init() - rcutree_cpu_report_dead() Add some documentation on this and refer to it from comments in the code explaining how QS reporting is not missed when these functions are concurrently running. I referred heavily to this post [1] about the need for the ofl_lock. [1] https://lore.kernel.org/all/20180924164443.GF4222@linux.ibm.com/ [ Applied paulmck feedback on moving documentation to Requirements.rst ] Link: https://lore.kernel.org/all/01b4d228-9416-43f8-a62e-124b92e8741a@paulmck-laptop/ Co-developed-by: "Paul E. McKenney" <paulmck@kernel.org> Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com> Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org> |
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| .. | ||
| Design | ||
| checklist.rst | ||
| index.rst | ||
| listRCU.rst | ||
| lockdep-splat.rst | ||
| lockdep.rst | ||
| NMI-RCU.rst | ||
| rcu.rst | ||
| rcu_dereference.rst | ||
| rcubarrier.rst | ||
| rculist_nulls.rst | ||
| rcuref.rst | ||
| RTFP.txt | ||
| stallwarn.rst | ||
| torture.rst | ||
| UP.rst | ||
| whatisRCU.rst | ||