It would be nice to validate that the caller of rcu_sync_is_idle()
holds the corresponding type of RCU read-side lock. Add the new
rcu_sync_ops->held() method and change rcu_sync_is_idle() to
WARN() if it returns false.
This obviously penalizes the readers (fast-path), but only if
CONFIG_PROVE_RCU.
Suggested-by: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
include/linux/rcusync.h | 6 ++++++
kernel/rcusync.c | 9 +++++++++
2 files changed, 15 insertions(+), 0 deletions(-)
diff --git a/include/linux/rcusync.h b/include/linux/rcusync.h
index 30c6037..ab787c1 100644
--- a/include/linux/rcusync.h
+++ b/include/linux/rcusync.h
@@ -7,6 +7,9 @@
struct rcu_sync_ops {
void (*sync)(void);
void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
+#ifdef CONFIG_PROVE_RCU
+ int (*held)(void);
+#endif
};
struct rcu_sync_struct {
@@ -22,6 +25,9 @@ struct rcu_sync_struct {
static inline bool rcu_sync_is_idle(struct rcu_sync_struct *rss)
{
+#ifdef CONFIG_PROVE_RCU
+ WARN_ON(!rss->ops->held());
+#endif
return !rss->gp_state; /* GP_IDLE */
}
diff --git a/kernel/rcusync.c b/kernel/rcusync.c
index 1cefb83..21cde9b 100644
--- a/kernel/rcusync.c
+++ b/kernel/rcusync.c
@@ -6,18 +6,27 @@ enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
#define rss_lock gp_wait.lock
+#ifdef CONFIG_PROVE_RCU
+#define __INIT_HELD(func) .held = func,
+#else
+#define __INIT_HELD(func)
+#endif
+
struct rcu_sync_ops rcu_sync_ops_array[] = {
[RCU_SYNC] = {
.sync = synchronize_rcu,
.call = call_rcu,
+ __INIT_HELD(rcu_read_lock_held)
},
[RCU_SCHED_SYNC] = {
.sync = synchronize_sched,
.call = call_rcu_sched,
+ __INIT_HELD(rcu_read_lock_sched_held)
},
[RCU_BH_SYNC] = {
.sync = synchronize_rcu_bh,
.call = call_rcu_bh,
+ __INIT_HELD(rcu_read_lock_bh_held)
},
};
--
1.5.5.1
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