diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2022-01-27 14:56:39 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2022-04-11 15:52:30 -0700 |
| commit | 99659f64b14e55cfa48980f5396f83820bafd028 (patch) | |
| tree | 6e773e1b172c394e1de48981f7abf189c92f39a8 /kernel/rcu | |
| parent | ee5e2448bceb9400aa27207f0c0220f9dedd85eb (diff) | |
srcu: Create concurrency-safe helper for initiating size transition
Once there are contention-initiated size transitions, it will be
possible for rcutorture to initiate a transition at the same time
as a contention-initiated transition. This commit therefore creates
a concurrency-safe helper function named srcu_transition_to_big() to
safely initiate size transitions.
Co-developed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/srcutree.c | 23 |
1 files changed, 21 insertions, 2 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 64993a172cff..c9460374d437 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -273,6 +273,25 @@ EXPORT_SYMBOL_GPL(init_srcu_struct); #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ /* + * Initiate an idempotent transition to SRCU_SIZE_BIG. + */ +static void srcu_transition_to_big(struct srcu_struct *ssp) +{ + unsigned long flags; + + /* Double-checked locking on ->srcu_size-state. */ + if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL) + return; + spin_lock_irqsave_rcu_node(ssp, flags); + if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL) { + spin_unlock_irqrestore_rcu_node(ssp, flags); + return; + } + smp_store_release(&ssp->srcu_size_state, SRCU_SIZE_ALLOC); + spin_unlock_irqrestore_rcu_node(ssp, flags); +} + +/* * First-use initialization of statically allocated srcu_struct * structure. Wiring up the combining tree is more than can be * done with compile-time initialization, so this check is added @@ -1523,8 +1542,8 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf) } pr_cont(" T(%ld,%ld)\n", s0, s1); } - if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && convert_to_big == 2) - WRITE_ONCE(ssp->srcu_size_state, SRCU_SIZE_ALLOC); + if (convert_to_big == 2) + srcu_transition_to_big(ssp); } EXPORT_SYMBOL_GPL(srcu_torture_stats_print); |