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rcu: Add full-sized polling for cond_sync_full()

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The cond_synchronize_rcu() API compresses 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 yet another member of the full-state RCU
grace-period polling API, which is the cond_synchronize_rcu_full()
function.  This uses up to three times the storage (rcu_gp_oldstate
structure instead of unsigned long), but is guaranteed not to miss
grace periods.

[ paulmck: Apply feedback from kernel test robot and Julia Lawall. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney
2022-08-04 13:46:05 -07:00
parent f21e014345
commit b6fe4917ae
4 changed files with 80 additions and 21 deletions
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5
include/linux/rcutiny.h
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@@ -44,6 +44,11 @@ static inline void cond_synchronize_rcu(unsigned long oldstate)
might_sleep();
}
static inline void cond_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
{
cond_synchronize_rcu(rgosp->rgos_norm);
}
static inline unsigned long start_poll_synchronize_rcu_expedited(void)
{
return start_poll_synchronize_rcu();