From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 27/30] rcu: Make nocb_gp_wait() double-check unexpected-callback warning
Date: Fri, 14 Feb 2020 15:56:04 -0800 [thread overview]
Message-ID: <20200214235607.13749-27-paulmck@kernel.org> (raw)
In-Reply-To: <20200214235536.GA13364@paulmck-ThinkPad-P72>
From: "Paul E. McKenney" <paulmck@kernel.org>
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>
---
kernel/rcu/tree_plugin.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 70b3c0f..36e71c9 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 ||
--
2.9.5
next prev parent reply other threads:[~2020-02-14 23:57 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 23:55 [PATCH tip/core/rcu 0/30] Miscellaneous fixes for v5.7 Paul E. McKenney
2020-02-14 23:55 ` [PATCH tip/core/rcu 01/30] nfs: Fix nfs_access_get_cached_rcu() sparse error paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 02/30] rcu: Warn on for_each_leaf_node_cpu_mask() from non-leaf paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 03/30] rcu: Fix exp_funnel_lock()/rcu_exp_wait_wake() datarace paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 04/30] rcu: Provide debug symbols and line numbers in KCSAN runs paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 05/30] rcu: Add WRITE_ONCE() to rcu_node ->qsmask update paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 06/30] rcu: Add WRITE_ONCE to rcu_node ->exp_seq_rq store paulmck
2020-02-15 3:47 ` Steven Rostedt
2020-02-15 10:58 ` Paul E. McKenney
2020-02-17 21:11 ` Joel Fernandes
2020-02-17 21:36 ` Paul E. McKenney
2020-02-14 23:55 ` [PATCH tip/core/rcu 07/30] rcu: Add READ_ONCE() to rcu_node ->gp_seq paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 08/30] rcu: Add WRITE_ONCE() to rcu_state ->gp_req_activity paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 09/30] rcu: Add WRITE_ONCE() to rcu_node ->qsmaskinitnext paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 10/30] locking/rtmutex: rcu: Add WRITE_ONCE() to rt_mutex ->owner paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 11/30] rcu: Add READ_ONCE() to rcu_segcblist ->tails[] paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 12/30] rcu: *_ONCE() for grace-period progress indicators paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 13/30] rcu: Fix typos in beginning comments paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 14/30] rcu: Add READ_ONCE() to rcu_data ->gpwrap paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 15/30] rcu: Add *_ONCE() to rcu_data ->rcu_forced_tick paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 16/30] rcu: Add *_ONCE() to rcu_node ->boost_kthread_status paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 17/30] timer: Use hlist_unhashed_lockless() in timer_pending() paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 18/30] rcu: Remove dead code from rcu_segcblist_insert_pend_cbs() paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 19/30] rcu: Add WRITE_ONCE() to rcu_state ->gp_start paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 20/30] rcu: Fix rcu_barrier_callback() race condition paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 21/30] rculist: Add brackets around cond argument in __list_check_rcu macro paulmck
2020-02-14 23:55 ` [PATCH tip/core/rcu 22/30] rcu: Don't flag non-starting GPs before GP kthread is running paulmck
2020-02-15 3:53 ` Steven Rostedt
2020-02-15 11:01 ` Paul E. McKenney
2020-02-15 13:42 ` Paul E. McKenney
2020-02-17 20:25 ` Steven Rostedt
2020-02-17 22:03 ` Paul E. McKenney
2020-02-17 22:21 ` Steven Rostedt
2020-02-17 23:03 ` Paul E. McKenney
2020-02-14 23:56 ` [PATCH tip/core/rcu 23/30] rcu: Add missing annotation for rcu_nocb_bypass_lock() paulmck
2020-02-14 23:56 ` [PATCH tip/core/rcu 24/30] rcu/nocb: Add missing annotation for rcu_nocb_bypass_unlock() paulmck
2020-02-14 23:56 ` [PATCH tip/core/rcu 25/30] rcu: Optimize and protect atomic_cmpxchg() loop paulmck
2020-02-14 23:56 ` [PATCH tip/core/rcu 26/30] rcu: Tighten rcu_lockdep_assert_cblist_protected() check paulmck
2020-02-14 23:56 ` paulmck [this message]
2020-02-14 23:56 ` [PATCH tip/core/rcu 28/30] rcu: Mark rcu_state.ncpus to detect concurrent writes paulmck
2020-02-14 23:56 ` [PATCH tip/core/rcu 29/30] rcu: Mark rcu_state.gp_seq " paulmck
2020-02-14 23:56 ` [PATCH tip/core/rcu 30/30] rcu: Make rcu_barrier() account for offline no-CBs CPUs paulmck
2020-02-25 10:24 ` Boqun Feng
2020-02-26 3:14 ` Paul E. McKenney
2020-02-26 4:18 ` Paul E. McKenney
2020-02-26 6:14 ` Boqun Feng
2020-02-26 15:02 ` Paul E. McKenney
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