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rcu: Make synchronize_rcu_expedited() fast path update .expedited_sequence

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This commit causes the early boot single-CPU synchronize_rcu_expedited()
fastpath to update the rcu_state structure's ->expedited_sequence
counter.  This will allow the full-state polled grace-period APIs to
detect all expedited grace periods without the need to track the special
combined polling-only counter, which is another step towards removing
the ->rgos_polled field from the rcu_gp_oldstate, thereby reducing its
size by one third.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-08-04 17:43:53 -07:00
parent e8755d2bde
commit 43ff97cc99
1 changed files with 6 additions and 0 deletions
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6
kernel/rcu/tree_exp.h
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@ -906,6 +906,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
void synchronize_rcu_expedited(void)
{
bool boottime = (rcu_scheduler_active == RCU_SCHEDULER_INIT);
unsigned long flags;
struct rcu_exp_work rew;
struct rcu_node *rnp;
unsigned long s;
@ -924,6 +925,11 @@ void synchronize_rcu_expedited(void)
// them, which allows reuse of ->gp_seq_polled_exp_snap.
rcu_poll_gp_seq_start_unlocked(&rcu_state.gp_seq_polled_exp_snap);
rcu_poll_gp_seq_end_unlocked(&rcu_state.gp_seq_polled_exp_snap);
local_irq_save(flags);
WARN_ON_ONCE(num_online_cpus() > 1);
rcu_state.expedited_sequence += (1 << RCU_SEQ_CTR_SHIFT);
local_irq_restore(flags);
return; // Context allows vacuous grace periods.
}