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

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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@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paul E. McKenney
2020-11-13 09:37:39 -08:00
committed by Greg Kroah-Hartman
parent f789de3be8
commit 641e1d8840
1 changed files with 11 additions and 6 deletions
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17
kernel/rcu/srcutiny.c
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@@ -151,6 +151,16 @@ void srcu_drive_gp(struct work_struct *wp)
} }
EXPORT_SYMBOL_GPL(srcu_drive_gp); 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, * Enqueue an SRCU callback on the specified srcu_struct structure,
* initiating grace-period processing if it is not already running. * initiating grace-period processing if it is not already running.
@@ -166,12 +176,7 @@ void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
*ssp->srcu_cb_tail = rhp; *ssp->srcu_cb_tail = rhp;
ssp->srcu_cb_tail = &rhp->next; ssp->srcu_cb_tail = &rhp->next;
local_irq_restore(flags); local_irq_restore(flags);
if (!READ_ONCE(ssp->srcu_gp_running)) { srcu_gp_start_if_needed(ssp);
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);
}
} }
EXPORT_SYMBOL_GPL(call_srcu); EXPORT_SYMBOL_GPL(call_srcu);