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| author | Joel Fernandes (Google) <joel@joelfernandes.org> | 2020-11-18 19:15:41 +0300 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2021-01-07 03:24:19 +0300 |
| commit | b4e6039e8af8c20dfbbdfcaebfcbd7c9d9ffe713 (patch) | |
| tree | a739b9f1aef750d312a7b0002a8db189c197477e | |
| parent | 3afe7fa535491ecd0382c3968dc2349602bff8a2 (diff) | |
| download | linux-b4e6039e8af8c20dfbbdfcaebfcbd7c9d9ffe713.tar.xz | |
rcu/segcblist: Add debug checks for segment lengths
This commit adds debug checks near the end of rcu_do_batch() that emit
warnings if an empty rcu_segcblist structure has non-zero segment counts,
or, conversely, if a non-empty structure has all-zero segment counts.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
[ paulmck: Fix queue/segment-length checks. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
| -rw-r--r-- | kernel/rcu/rcu_segcblist.c | 12 | ||||
| -rw-r--r-- | kernel/rcu/rcu_segcblist.h | 3 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 8 |
3 files changed, 21 insertions, 2 deletions
diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c index 1e80a0a9036a..89e0dff890bf 100644 --- a/kernel/rcu/rcu_segcblist.c +++ b/kernel/rcu/rcu_segcblist.c @@ -94,6 +94,18 @@ static long rcu_segcblist_get_seglen(struct rcu_segcblist *rsclp, int seg) return READ_ONCE(rsclp->seglen[seg]); } +/* Return number of callbacks in segmented callback list by summing seglen. */ +long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp) +{ + long len = 0; + int i; + + for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++) + len += rcu_segcblist_get_seglen(rsclp, i); + + return len; +} + /* Set the length of a segment of the rcu_segcblist structure. */ static void rcu_segcblist_set_seglen(struct rcu_segcblist *rsclp, int seg, long v) { diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h index cd35c9faaf51..18e101de8747 100644 --- a/kernel/rcu/rcu_segcblist.h +++ b/kernel/rcu/rcu_segcblist.h @@ -15,6 +15,9 @@ static inline long rcu_cblist_n_cbs(struct rcu_cblist *rclp) return READ_ONCE(rclp->len); } +/* Return number of callbacks in segmented callback list by summing seglen. */ +long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp); + void rcu_cblist_init(struct rcu_cblist *rclp); void rcu_cblist_enqueue(struct rcu_cblist *rclp, struct rcu_head *rhp); void rcu_cblist_flush_enqueue(struct rcu_cblist *drclp, diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 6bf269c91393..8086c0467c15 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2434,6 +2434,7 @@ int rcutree_dead_cpu(unsigned int cpu) static void rcu_do_batch(struct rcu_data *rdp) { int div; + bool __maybe_unused empty; unsigned long flags; const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist); struct rcu_head *rhp; @@ -2548,9 +2549,12 @@ static void rcu_do_batch(struct rcu_data *rdp) * The following usually indicates a double call_rcu(). To track * this down, try building with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y. */ - WARN_ON_ONCE(count == 0 && !rcu_segcblist_empty(&rdp->cblist)); + empty = rcu_segcblist_empty(&rdp->cblist); + WARN_ON_ONCE(count == 0 && !empty); WARN_ON_ONCE(!IS_ENABLED(CONFIG_RCU_NOCB_CPU) && - count != 0 && rcu_segcblist_empty(&rdp->cblist)); + count != 0 && empty); + WARN_ON_ONCE(count == 0 && rcu_segcblist_n_segment_cbs(&rdp->cblist) != 0); + WARN_ON_ONCE(!empty && rcu_segcblist_n_segment_cbs(&rdp->cblist) == 0); rcu_nocb_unlock_irqrestore(rdp, flags); |