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rcu: Warn when srcu_read_lock() is used in an extended quiescent state

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Catch SRCU up to the other variants of RCU by making PROVE_RCU
complain if either srcu_read_lock() or srcu_read_lock_held() are
used from within RCU-idle mode.

Frederic reworked this to allow for the new versions of his patches
that check for extended quiescent states.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney 2011-10-07 18:22:04 +02:00 committed by Paul E. McKenney
parent d8ab29f8be
commit ff195cb69b
1 changed files with 23 additions and 13 deletions
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36
include/linux/srcu.h
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@ -28,6 +28,7 @@
#define _LINUX_SRCU_H
#include <linux/mutex.h>
#include <linux/rcupdate.h>
struct srcu_struct_array {
int c[2];
@ -60,18 +61,10 @@ int __init_srcu_struct(struct srcu_struct *sp, const char *name,
__init_srcu_struct((sp), #sp, &__srcu_key); \
})
# define srcu_read_acquire(sp) \
lock_acquire(&(sp)->dep_map, 0, 0, 2, 1, NULL, _THIS_IP_)
# define srcu_read_release(sp) \
lock_release(&(sp)->dep_map, 1, _THIS_IP_)
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
int init_srcu_struct(struct srcu_struct *sp);
# define srcu_read_acquire(sp) do { } while (0)
# define srcu_read_release(sp) do { } while (0)
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
void cleanup_srcu_struct(struct srcu_struct *sp);
@ -90,12 +83,29 @@ long srcu_batches_completed(struct srcu_struct *sp);
* read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
* this assumes we are in an SRCU read-side critical section unless it can
* prove otherwise.
*
* Note that if the CPU is in the idle loop from an RCU point of view
* (ie: that we are in the section between rcu_idle_enter() and
* rcu_idle_exit()) then srcu_read_lock_held() returns false even if
* the CPU did an srcu_read_lock(). The reason for this is that RCU
* ignores CPUs that are in such a section, considering these as in
* extended quiescent state, so such a CPU is effectively never in an
* RCU read-side critical section regardless of what RCU primitives it
* invokes. This state of affairs is required --- we need to keep an
* RCU-free window in idle where the CPU may possibly enter into low
* power mode. This way we can notice an extended quiescent state to
* other CPUs that started a grace period. Otherwise we would delay any
* grace period as long as we run in the idle task.
*/
static inline int srcu_read_lock_held(struct srcu_struct *sp)
{
if (debug_locks)
return lock_is_held(&sp->dep_map);
return 1;
if (rcu_is_cpu_idle())
return 0;
if (!debug_locks)
return 1;
return lock_is_held(&sp->dep_map);
}
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
@ -150,7 +160,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
{
int retval = __srcu_read_lock(sp);
srcu_read_acquire(sp);
rcu_lock_acquire(&(sp)->dep_map);
return retval;
}
@ -164,7 +174,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
__releases(sp)
{
srcu_read_release(sp);
rcu_lock_release(&(sp)->dep_map);
__srcu_read_unlock(sp, idx);
}