diff options
| -rw-r--r-- | include/linux/rcutiny.h | 10 | ||||
| -rw-r--r-- | include/linux/rcutree.h | 2 | ||||
| -rw-r--r-- | kernel/rcu/rcutorture.c | 2 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 52 |
4 files changed, 66 insertions, 0 deletions
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 3df6c1ec4e25..ff968b7af3a4 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -37,6 +37,16 @@ static inline void cond_synchronize_rcu(unsigned long oldstate) might_sleep(); } +static inline unsigned long get_state_synchronize_sched(void) +{ + return 0; +} + +static inline void cond_synchronize_sched(unsigned long oldstate) +{ + might_sleep(); +} + static inline void rcu_barrier_bh(void) { wait_rcu_gp(call_rcu_bh); diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 456879143f89..5abec82f325e 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -76,6 +76,8 @@ void rcu_barrier_bh(void); void rcu_barrier_sched(void); unsigned long get_state_synchronize_rcu(void); void cond_synchronize_rcu(unsigned long oldstate); +unsigned long get_state_synchronize_sched(void); +void cond_synchronize_sched(unsigned long oldstate); extern unsigned long rcutorture_testseq; extern unsigned long rcutorture_vernum; diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 59e32684c23b..0f2cb55f0ab3 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -635,6 +635,8 @@ static struct rcu_torture_ops sched_ops = { .deferred_free = rcu_sched_torture_deferred_free, .sync = synchronize_sched, .exp_sync = synchronize_sched_expedited, + .get_state = get_state_synchronize_sched, + .cond_sync = cond_synchronize_sched, .call = call_rcu_sched, .cb_barrier = rcu_barrier_sched, .fqs = rcu_sched_force_quiescent_state, diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8b5dd8ba9495..9629298eea24 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3253,6 +3253,58 @@ void cond_synchronize_rcu(unsigned long oldstate) } EXPORT_SYMBOL_GPL(cond_synchronize_rcu); +/** + * get_state_synchronize_sched - Snapshot current RCU-sched state + * + * Returns a cookie that is used by a later call to cond_synchronize_sched() + * to determine whether or not a full grace period has elapsed in the + * meantime. + */ +unsigned long get_state_synchronize_sched(void) +{ + /* + * Any prior manipulation of RCU-protected data must happen + * before the load from ->gpnum. + */ + smp_mb(); /* ^^^ */ + + /* + * Make sure this load happens before the purportedly + * time-consuming work between get_state_synchronize_sched() + * and cond_synchronize_sched(). + */ + return smp_load_acquire(&rcu_sched_state.gpnum); +} +EXPORT_SYMBOL_GPL(get_state_synchronize_sched); + +/** + * cond_synchronize_sched - Conditionally wait for an RCU-sched grace period + * + * @oldstate: return value from earlier call to get_state_synchronize_sched() + * + * If a full RCU-sched grace period has elapsed since the earlier call to + * get_state_synchronize_sched(), just return. Otherwise, invoke + * synchronize_sched() to wait for a full grace period. + * + * Yes, this function does not take counter wrap into account. But + * counter wrap is harmless. If the counter wraps, we have waited for + * more than 2 billion grace periods (and way more on a 64-bit system!), + * so waiting for one additional grace period should be just fine. + */ +void cond_synchronize_sched(unsigned long oldstate) +{ + unsigned long newstate; + + /* + * Ensure that this load happens before any RCU-destructive + * actions the caller might carry out after we return. + */ + newstate = smp_load_acquire(&rcu_sched_state.completed); + if (ULONG_CMP_GE(oldstate, newstate)) + synchronize_sched(); +} +EXPORT_SYMBOL_GPL(cond_synchronize_sched); + static int synchronize_sched_expedited_cpu_stop(void *data) { /* |