Commit 1a893c71 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

srcu: Provide internal interface to start a Tiny SRCU grace period 

There is a need for a polling interface for SRCU grace periods.
This polling needs to initiate an SRCU grace period without
having to queue (and manage) a callback.  This commit therefore
splits the Tiny SRCU call_srcu() function into callback-queuing and
start-grace-period portions, with the latter in a new function named
srcu_gp_start_if_needed().

Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/


Reported-by: default avatarKent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: default avatarNeeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 74612a07

kernel/rcu/srcutiny.c

+11 −6
Original line number Diff line number Diff line
@@ -152,6 +152,16 @@ void srcu_drive_gp(struct work_struct *wp) 
}

EXPORT_SYMBOL_GPL(srcu_drive_gp);



static void srcu_gp_start_if_needed(struct srcu_struct *ssp)

{

	if (!READ_ONCE(ssp->srcu_gp_running)) {

		if (likely(srcu_init_done))

			schedule_work(&ssp->srcu_work);

		else if (list_empty(&ssp->srcu_work.entry))

			list_add(&ssp->srcu_work.entry, &srcu_boot_list);

	}

}



/*

 * Enqueue an SRCU callback on the specified srcu_struct structure,

 * initiating grace-period processing if it is not already running.
@@ -167,12 +177,7 @@ void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp, 
	*ssp->srcu_cb_tail = rhp;

	ssp->srcu_cb_tail = &rhp->next;

	local_irq_restore(flags);

	if (!READ_ONCE(ssp->srcu_gp_running)) {

		if (likely(srcu_init_done))

			schedule_work(&ssp->srcu_work);

		else if (list_empty(&ssp->srcu_work.entry))

			list_add(&ssp->srcu_work.entry, &srcu_boot_list);

	}

	srcu_gp_start_if_needed(ssp);

}

EXPORT_SYMBOL_GPL(call_srcu);