6.5-stable review patch. If anyone has any objections, please let me know.
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From: Frederic Weisbecker frederic@kernel.org
[ Upstream commit 8a77f38bcd28d3c22ab7dd8eff3f299d43c00411 ]
Acceleration in SRCU happens on enqueue time for each new callback. This operation is expected not to fail and therefore any similar attempt from other places shouldn't find any remaining callbacks to accelerate.
Moreover accelerations performed beyond enqueue time are error prone because rcu_seq_snap() then may return the snapshot for a new grace period that is not going to be started.
Remove these dangerous and needless accelerations and introduce instead assertions reporting leaking unaccelerated callbacks beyond enqueue time.
Co-developed-by: Yong He alexyonghe@tencent.com Signed-off-by: Yong He alexyonghe@tencent.com Co-developed-by: Joel Fernandes (Google) joel@joelfernandes.org Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org Co-developed-by: Neeraj upadhyay Neeraj.Upadhyay@amd.com Signed-off-by: Neeraj upadhyay Neeraj.Upadhyay@amd.com Reviewed-by: Like Xu likexu@tencent.com Signed-off-by: Frederic Weisbecker frederic@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/rcu/srcutree.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 7522517b63b6f..2f770a9a2a13a 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -782,8 +782,7 @@ static void srcu_gp_start(struct srcu_struct *ssp) spin_lock_rcu_node(sdp); /* Interrupts already disabled. */ rcu_segcblist_advance(&sdp->srcu_cblist, rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq)); - (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, - rcu_seq_snap(&ssp->srcu_sup->srcu_gp_seq)); + WARN_ON_ONCE(!rcu_segcblist_segempty(&sdp->srcu_cblist, RCU_NEXT_TAIL)); spin_unlock_rcu_node(sdp); /* Interrupts remain disabled. */ WRITE_ONCE(ssp->srcu_sup->srcu_gp_start, jiffies); WRITE_ONCE(ssp->srcu_sup->srcu_n_exp_nodelay, 0); @@ -1719,6 +1718,7 @@ static void srcu_invoke_callbacks(struct work_struct *work) ssp = sdp->ssp; rcu_cblist_init(&ready_cbs); spin_lock_irq_rcu_node(sdp); + 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)); if (sdp->srcu_cblist_invoking || @@ -1748,8 +1748,6 @@ static void srcu_invoke_callbacks(struct work_struct *work) */ spin_lock_irq_rcu_node(sdp); rcu_segcblist_add_len(&sdp->srcu_cblist, -len); - (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, - rcu_seq_snap(&ssp->srcu_sup->srcu_gp_seq)); sdp->srcu_cblist_invoking = false; more = rcu_segcblist_ready_cbs(&sdp->srcu_cblist); spin_unlock_irq_rcu_node(sdp);