Xen's RCU implementation relies on no softirq handling taking place
while being in a RCU critical section. Add ASSERT()s in debug builds
in order to catch any violations.
For that purpose modify rcu_read_[un]lock() to use a dedicated percpu
counter instead of preempt_[en|dis]able() as this enables to test
that condition in __do_softirq() (ASSERT_NOT_IN_ATOMIC() is not
usable there due to __cpu_up() calling process_pending_softirqs()
while holding the cpu hotplug lock).
Dropping the now no longer needed #include of preempt.h in rcupdate.h
requires adding it in some sources.
While at it switch the rcu_read_[un]lock() implementation to static
inline functions instead of macros.
Signed-off-by: Juergen Gross
---
V3:
- add barriers to rcu_[en|dis]able() (Roger Pau Monné)
- add rcu_quiesce_allowed() to ASSERT_NOT_IN_ATOMIC (Roger Pau Monné)
- convert macros to static inline functions
- add sanity check in rcu_read_unlock()
---
xen/common/multicall.c | 1 +
xen/common/preempt.c | 5 -
xen/common/rcupdate.c | 4
xen/common/softirq.c | 2 ++
xen/common/wait.c | 1 +
xen/include/xen/rcupdate.h | 45 +
6 files changed, 53 insertions(+), 5 deletions(-)
diff --git a/xen/common/multicall.c b/xen/common/multicall.c
index 5a199ebf8f..67f1a23485 100644
--- a/xen/common/multicall.c
+++ b/xen/common/multicall.c
@@ -10,6 +10,7 @@
#include
#include
#include
+#include
#include
#include
#include
diff --git a/xen/common/preempt.c b/xen/common/preempt.c
index 3b4178fd44..8a351e644b 100644
--- a/xen/common/preempt.c
+++ b/xen/common/preempt.c
@@ -21,13 +21,15 @@
#include
#include
+#include
#include
DEFINE_PER_CPU(unsigned int, __preempt_count);
bool_t in_atomic(void)
{
-return preempt_count() || in_irq() || !local_irq_is_enabled();
+return preempt_count() || in_irq() || !local_irq_is_enabled() ||
+ !rcu_quiesce_allowed();
}
#ifndef NDEBUG
@@ -36,5 +38,6 @@ void ASSERT_NOT_IN_ATOMIC(void)
ASSERT(!preempt_count());
ASSERT(!in_irq());
ASSERT(local_irq_is_enabled());
+ASSERT(rcu_quiesce_allowed());
}
#endif
diff --git a/xen/common/rcupdate.c b/xen/common/rcupdate.c
index 27d597bbeb..d1cc2f0a98 100644
--- a/xen/common/rcupdate.c
+++ b/xen/common/rcupdate.c
@@ -46,6 +46,10 @@
#include
#include
+#ifndef NDEBUG
+DEFINE_PER_CPU(unsigned int, rcu_lock_cnt);
+#endif
+
/* Global control variables for rcupdate callback mechanism. */
static struct rcu_ctrlblk {
long cur; /* Current batch number. */
diff --git a/xen/common/softirq.c b/xen/common/softirq.c
index 30beb27ae9..fd90b8511d 100644
--- a/xen/common/softirq.c
+++ b/xen/common/softirq.c
@@ -30,6 +30,8 @@ static void __do_softirq(unsigned long ignore_mask, bool
rcu_allowed)
unsigned int i, cpu;
unsigned long pending;
+ASSERT(!rcu_allowed || rcu_quiesce_allowed());
+
for ( ; ; )
{
/*
diff --git a/xen/common/wait.c b/xen/common/wait.c
index 24716e7676..9cdb174036 100644
--- a/xen/common/wait.c
+++ b/xen/common/wait.c
@@ -19,6 +19,7 @@
* along with this program; If not, see .
*/
+#include
#include
#include
#include
diff --git a/xen/include/xen/rcupdate.h b/xen/include/xen/rcupdate.h
index 31c8b86d13..9f6d420898 100644
--- a/xen/include/xen/rcupdate.h
+++ b/xen/include/xen/rcupdate.h
@@ -34,10 +34,40 @@
#include
#include
#include
-#include
+#include
+#include
#define __rcu
+#ifndef NDEBUG
+DECLARE_PER_CPU(unsigned int, rcu_lock_cnt);
+
+static inline void rcu_quiesce_disable(void)
+{
+this_cpu(rcu_lock_cnt)++;
+arch_lock_acquire_barrier();
+}
+
+static inline void rcu_quiesce_enable(void)
+{
+arch_lock_release_barrier();
+this_cpu(rcu_lock_cnt)--;
+}
+
+static inline bool rcu_quiesce_allowed(void)
+{
+return !this_cpu(rcu_lock_cnt);
+}
+
+#else
+static inline void rcu_quiesce_disable(void) { }
+static inline void rcu_quiesce_enable(void) { }
+static inline bool rcu_quiesce_allowed(void)
+{
+return true;
+}
+#endif
+
/**
* struct rcu_head - callback structure for use with RCU
* @next: next update requests in a list
@@ -91,16 +121,23 @@ typedef struct _rcu_read_lock rcu_read_lock_t;
* will be deferred until the outermost RCU read-side critical section
* completes.
*
- * It is illegal to block while in an RCU read-side critical section.
+ * It is illegal to process softirqs while in an RCU read-side critical
section.
*/
-#define rcu_read_lock(x) ({ ((void)(x)); preempt_disable(); })
+static inline void rcu_read_lock(rcu_read_lock_t *lock)
+{
+rcu_quiesce_disable();
+}
/**
* rcu_read_unlock - marks the end of an RCU read-side critical section.
*
* See rcu_read_lock() for more information.
*/
-#define rcu_read_unlock(x) ({ ((void)(x)); preempt_enable(); })
+static inline void rcu_read_unlock(rcu_read_lock_t *lock)
+{
+ASSERT(!rcu_quiesc
