On 7/7/2025 10:22 AM, Frederic Weisbecker wrote: > Le Sun, Jul 06, 2025 at 11:32:08PM -0400, Joel Fernandes a écrit : >> 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@xxxxxxxxxxxxx/ >> >> [ 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@xxxxxxxxxx> >> Signed-off-by: Joel Fernandes <joelagnelf@xxxxxxxxxx> > > Very nice and welcome!!! > > Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx> > Thanks, glad you like it. I figured this stuff is better off in the kernel documentation than rotting in my notes ;-) And lets continue to keep the discussions going ;-) thanks! - Joel
