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authorFrederic Weisbecker <frederic@kernel.org>2023-10-04 01:29:03 +0200
committerNeeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>2023-12-12 02:41:17 +0530
commitc21357e4461f3f9c8ff93302906b5372411ee108 (patch)
tree34ccce4bed9c80e4ab0eb2fb9ce91c5f07877789 /kernel/rcu/srcutree.c
parent94c55b9e21979daa88e190bf971c47432a818ebe (diff)
srcu: Explain why callbacks invocations can't run concurrently
If an SRCU barrier is queued while callbacks are running and a new callbacks invocator for the same sdp were to run concurrently, the RCU barrier might execute too early. As this requirement is non-obvious, make sure to keep a record. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Diffstat (limited to 'kernel/rcu/srcutree.c')
-rw-r--r--kernel/rcu/srcutree.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 2bfc8ed1eed2..0351a4e83529 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1715,6 +1715,11 @@ static void srcu_invoke_callbacks(struct work_struct *work)
WARN_ON_ONCE(!rcu_segcblist_segempty(&sdp->srcu_cblist, RCU_NEXT_TAIL));
rcu_segcblist_advance(&sdp->srcu_cblist,
rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq));
+ /*
+ * Although this function is theoretically re-entrant, concurrent
+ * callbacks invocation is disallowed to avoid executing an SRCU barrier
+ * too early.
+ */
if (sdp->srcu_cblist_invoking ||
!rcu_segcblist_ready_cbs(&sdp->srcu_cblist)) {
spin_unlock_irq_rcu_node(sdp);
@@ -1745,6 +1750,7 @@ static void srcu_invoke_callbacks(struct work_struct *work)
sdp->srcu_cblist_invoking = false;
more = rcu_segcblist_ready_cbs(&sdp->srcu_cblist);
spin_unlock_irq_rcu_node(sdp);
+ /* An SRCU barrier or callbacks from previous nesting work pending */
if (more)
srcu_schedule_cbs_sdp(sdp, 0);
}