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| author | Frederic Weisbecker <frederic@kernel.org> | 2023-10-04 01:29:03 +0200 |
|---|---|---|
| committer | Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com> | 2023-12-11 22:11:17 +0100 |
| commit | c21357e4461f3f9c8ff93302906b5372411ee108 (patch) | |
| tree | 34ccce4bed9c80e4ab0eb2fb9ce91c5f07877789 /kernel/rcu/srcutree.c | |
| parent | srcu: No need to advance/accelerate if no callback enqueued (diff) | |
| download | linux-c21357e4461f3f9c8ff93302906b5372411ee108.tar.xz linux-c21357e4461f3f9c8ff93302906b5372411ee108.zip | |
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.c | 6 |
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); } |