From: Paul E. McKenney <paulmck@xxxxxxxxxx> commit 1a893c711a600ab57526619b56e6f6b7be00956e upstream. 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@xxxxxxxxxxxxxx/ Reported-by: Kent Overstreet <kent.overstreet@xxxxxxxxx> Reviewed-by: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/rcu/srcutiny.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -151,6 +151,16 @@ void srcu_drive_gp(struct work_struct *w } 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. @@ -166,12 +176,7 @@ void call_srcu(struct srcu_struct *ssp, *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);
