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| author | Paul E. McKenney <paulmck@kernel.org> | 2020-02-04 14:55:29 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-02-20 15:58:23 -0800 |
| commit | 3d05031ae6de6ad084aa41263aed1343065233d5 (patch) | |
| tree | 4f413b88d90e48852037943c1470c46076e94a82 /kernel/rcu | |
| parent | 13817dd589f426aee9c36e3670e7cb2a7f067d23 (diff) | |
| download | linux-3d05031ae6de6ad084aa41263aed1343065233d5.tar.bz2 | |
rcu: Make nocb_gp_wait() double-check unexpected-callback warning
Currently, nocb_gp_wait() unconditionally complains if there is a
callback not already associated with a grace period. This assumes that
either there was no such callback initially on the one hand, or that
the rcu_advance_cbs() function assigned all such callbacks to a grace
period on the other. However, in theory there are some situations that
would prevent rcu_advance_cbs() from assigning all of the callbacks.
This commit therefore checks for unassociated callbacks immediately after
rcu_advance_cbs() returns, while the corresponding rcu_node structure's
->lock is still held. If there are unassociated callbacks at that point,
the subsequent WARN_ON_ONCE() is disabled.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 70b3c0f4ea37..36e71c99970a 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1931,6 +1931,7 @@ static void nocb_gp_wait(struct rcu_data *my_rdp) struct rcu_data *rdp; struct rcu_node *rnp; unsigned long wait_gp_seq = 0; // Suppress "use uninitialized" warning. + bool wasempty = false; /* * Each pass through the following loop checks for CBs and for the @@ -1970,10 +1971,13 @@ static void nocb_gp_wait(struct rcu_data *my_rdp) rcu_seq_done(&rnp->gp_seq, cur_gp_seq))) { raw_spin_lock_rcu_node(rnp); /* irqs disabled. */ needwake_gp = rcu_advance_cbs(rnp, rdp); + wasempty = rcu_segcblist_restempty(&rdp->cblist, + RCU_NEXT_READY_TAIL); raw_spin_unlock_rcu_node(rnp); /* irqs disabled. */ } // Need to wait on some grace period? - WARN_ON_ONCE(!rcu_segcblist_restempty(&rdp->cblist, + WARN_ON_ONCE(wasempty && + !rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)); if (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq)) { if (!needwait_gp || |