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rcu: Mark accesses to rcu_state.n_force_qs

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commit 2431774f04d1050292054c763070021bade7b151 upstream.

This commit marks accesses to the rcu_state.n_force_qs.  These data
races are hard to make happen, but syzkaller was equal to the task.

Reported-by: syzbot+e08a83a1940ec3846cd5@syzkaller.appspotmail.com
Acked-by: Marco Elver <elver@google.com>
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
2021-07-20 06:16:27 -07:00
committed by Greg Kroah-Hartman
parent a9078e7914
commit 70692b0620
1 changed files with 5 additions and 5 deletions
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10
kernel/rcu/tree.c
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@@ -1888,7 +1888,7 @@ static void rcu_gp_fqs(bool first_time)
struct rcu_node *rnp = rcu_get_root(); struct rcu_node *rnp = rcu_get_root();
WRITE_ONCE(rcu_state.gp_activity, jiffies); WRITE_ONCE(rcu_state.gp_activity, jiffies);
rcu_state.n_force_qs++; WRITE_ONCE(rcu_state.n_force_qs, rcu_state.n_force_qs + 1);
if (first_time) { if (first_time) {
/* Collect dyntick-idle snapshots. */ /* Collect dyntick-idle snapshots. */
force_qs_rnp(dyntick_save_progress_counter); force_qs_rnp(dyntick_save_progress_counter);
@@ -2530,7 +2530,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
/* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
if (count == 0 && rdp->qlen_last_fqs_check != 0) { if (count == 0 && rdp->qlen_last_fqs_check != 0) {
rdp->qlen_last_fqs_check = 0; rdp->qlen_last_fqs_check = 0;
rdp->n_force_qs_snap = rcu_state.n_force_qs; rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
} else if (count < rdp->qlen_last_fqs_check - qhimark) } else if (count < rdp->qlen_last_fqs_check - qhimark)
rdp->qlen_last_fqs_check = count; rdp->qlen_last_fqs_check = count;
@@ -2876,10 +2876,10 @@ static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head,
} else { } else {
/* Give the grace period a kick. */ /* Give the grace period a kick. */
rdp->blimit = DEFAULT_MAX_RCU_BLIMIT; rdp->blimit = DEFAULT_MAX_RCU_BLIMIT;
if (rcu_state.n_force_qs == rdp->n_force_qs_snap && if (READ_ONCE(rcu_state.n_force_qs) == rdp->n_force_qs_snap &&
rcu_segcblist_first_pend_cb(&rdp->cblist) != head) rcu_segcblist_first_pend_cb(&rdp->cblist) != head)
rcu_force_quiescent_state(); rcu_force_quiescent_state();
rdp->n_force_qs_snap = rcu_state.n_force_qs; rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist);
} }
} }
@@ -3986,7 +3986,7 @@ int rcutree_prepare_cpu(unsigned int cpu)
/* Set up local state, ensuring consistent view of global state. */ /* Set up local state, ensuring consistent view of global state. */
raw_spin_lock_irqsave_rcu_node(rnp, flags); raw_spin_lock_irqsave_rcu_node(rnp, flags);
rdp->qlen_last_fqs_check = 0; rdp->qlen_last_fqs_check = 0;
rdp->n_force_qs_snap = rcu_state.n_force_qs; rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
rdp->blimit = blimit; rdp->blimit = blimit;
if (rcu_segcblist_empty(&rdp->cblist) && /* No early-boot CBs? */ if (rcu_segcblist_empty(&rdp->cblist) && /* No early-boot CBs? */
!rcu_segcblist_is_offloaded(&rdp->cblist)) !rcu_segcblist_is_offloaded(&rdp->cblist))