rcu: Add full-sized polling for get_completed*() and poll_state*()

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The get_completed_synchronize_rcu() and poll_state_synchronize_rcu()
APIs compress the combined expedited and normal grace-period states into a
single unsigned long, which conserves storage, but can miss grace periods
in certain cases involving overlapping normal and expedited grace periods.
Missing the occasional grace period is usually not a problem, but there
are use cases that care about each and every grace period.

This commit therefore adds the first members of the full-state RCU
grace-period polling API, namely the get_completed_synchronize_rcu_full()
and poll_state_synchronize_rcu_full() functions.  These use up to three
times the storage (rcu_gp_oldstate structure instead of unsigned long),
but which are guaranteed not to miss grace periods, at least in situations
where the single-CPU grace-period optimization does not apply.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

...

This commit is contained in:

Paul E. McKenney 2022-07-28 15:37:05 -07:00

parent 568035b01c

commit 91a967fd69

6 changed files with 111 additions and 4 deletions

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3

include/linux/rcupdate.h

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9

include/linux/rcutiny.h

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8

include/linux/rcutree.h

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9

kernel/rcu/rcutorture.c

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10

kernel/rcu/tiny.c

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76

kernel/rcu/tree.c

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