From: Oleg Nesterov <o...@redhat.com>
This commit validates that the caller of rcu_sync_is_idle() holds the
corresponding type of RCU read-side lock, but only in kernels built
with CONFIG_PROVE_RCU=y. This validation is carried out via a new
rcu_sync_ops->held() method that is checked within rcu_sync_is_idle().
Note that although this does add code to the fast path, it only does so
in kernels built with CONFIG_PROVE_RCU=y.
Suggested-by: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <o...@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
---
include/linux/rcu_sync.h | 6 ++++++
kernel/rcu/sync.c | 20 ++++++++++++++++++++
2 files changed, 26 insertions(+)
diff --git a/include/linux/rcu_sync.h b/include/linux/rcu_sync.h
index c6d2272c4459..c55a070b2592 100644
--- a/include/linux/rcu_sync.h
+++ b/include/linux/rcu_sync.h
@@ -40,6 +40,8 @@ struct rcu_sync {
enum rcu_sync_type gp_type;
};
+extern bool __rcu_sync_is_idle(struct rcu_sync *);
+
/**
* rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
* @rsp: Pointer to rcu_sync structure to use for synchronization
@@ -50,7 +52,11 @@ struct rcu_sync {
*/
static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
{
+#ifdef CONFIG_PROVE_RCU
+ return __rcu_sync_is_idle(rss);
+#else
return !rsp->gp_state; /* GP_IDLE */
+#endif
}
extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c
index 5a9aa4c394f1..26b2629e731e 100644
--- a/kernel/rcu/sync.c
+++ b/kernel/rcu/sync.c
@@ -23,21 +23,33 @@
#include <linux/rcu_sync.h>
#include <linux/sched.h>
+#ifdef CONFIG_PROVE_RCU
+#define __INIT_HELD(func) .held = func,
+#else
+#define __INIT_HELD(func)
+#endif
+
static const struct {
void (*sync)(void);
void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
+#ifdef CONFIG_PROVE_RCU
+ int (*held)(void);
+#endif
} gp_ops[] = {
[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)
},
};
@@ -46,6 +58,13 @@ enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
#define rss_lock gp_wait.lock
+#ifdef CONFIG_PROVE_RCU
+bool __rcu_sync_is_idle(struct rcu_sync *rsp)
+{
+ WARN_ON(!gp_ops[rsp->gp_type].held());
+ return rsp->gp_state == GP_IDLE;
+}
+
/**
* rcu_sync_init() - Initialize an rcu_sync structure
* @rsp: Pointer to rcu_sync structure to be initialized
@@ -57,6 +76,7 @@ void rcu_sync_init(struct rcu_sync *rsp, enum rcu_sync_type
type)
init_waitqueue_head(&rsp->gp_wait);
rsp->gp_type = type;
}
+#endif
/**
* rcu_sync_enter() - Force readers onto slowpath
--
1.8.1.5
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