diff options
Diffstat (limited to 'kernel/rcu/tree.c')
| -rw-r--r-- | kernel/rcu/tree.c | 40 |
1 files changed, 38 insertions, 2 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 0b0dd9e1f057..e8a4b720d7d2 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -80,6 +80,15 @@ static void rcu_sr_normal_gp_cleanup_work(struct work_struct *); static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = { .gpwrap = true, }; + +int rcu_get_gpwrap_count(int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + + return READ_ONCE(rdp->gpwrap_count); +} +EXPORT_SYMBOL_GPL(rcu_get_gpwrap_count); + static struct rcu_state rcu_state = { .level = { &rcu_state.node[0] }, .gp_state = RCU_GP_IDLE, @@ -757,6 +766,25 @@ void rcu_request_urgent_qs_task(struct task_struct *t) smp_store_release(per_cpu_ptr(&rcu_data.rcu_urgent_qs, cpu), true); } +static unsigned long seq_gpwrap_lag = ULONG_MAX / 4; + +/** + * rcu_set_gpwrap_lag - Set RCU GP sequence overflow lag value. + * @lag_gps: Set overflow lag to this many grace period worth of counters + * which is used by rcutorture to quickly force a gpwrap situation. + * @lag_gps = 0 means we reset it back to the boot-time value. + */ +void rcu_set_gpwrap_lag(unsigned long lag_gps) +{ + unsigned long lag_seq_count; + + lag_seq_count = (lag_gps == 0) + ? ULONG_MAX / 4 + : lag_gps << RCU_SEQ_CTR_SHIFT; + WRITE_ONCE(seq_gpwrap_lag, lag_seq_count); +} +EXPORT_SYMBOL_GPL(rcu_set_gpwrap_lag); + /* * When trying to report a quiescent state on behalf of some other CPU, * it is our responsibility to check for and handle potential overflow @@ -767,9 +795,11 @@ void rcu_request_urgent_qs_task(struct task_struct *t) static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp) { raw_lockdep_assert_held_rcu_node(rnp); - if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + ULONG_MAX / 4, - rnp->gp_seq)) + if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + seq_gpwrap_lag, + rnp->gp_seq)) { WRITE_ONCE(rdp->gpwrap, true); + WRITE_ONCE(rdp->gpwrap_count, READ_ONCE(rdp->gpwrap_count) + 1); + } if (ULONG_CMP_LT(rdp->rcu_iw_gp_seq + ULONG_MAX / 4, rnp->gp_seq)) rdp->rcu_iw_gp_seq = rnp->gp_seq + ULONG_MAX / 4; } @@ -1770,6 +1800,7 @@ static noinline_for_stack bool rcu_gp_init(void) struct rcu_data *rdp; struct rcu_node *rnp = rcu_get_root(); bool start_new_poll; + unsigned long old_gp_seq; WRITE_ONCE(rcu_state.gp_activity, jiffies); raw_spin_lock_irq_rcu_node(rnp); @@ -1797,7 +1828,12 @@ static noinline_for_stack bool rcu_gp_init(void) */ start_new_poll = rcu_sr_normal_gp_init(); /* Record GP times before starting GP, hence rcu_seq_start(). */ + old_gp_seq = rcu_state.gp_seq; rcu_seq_start(&rcu_state.gp_seq); + /* Ensure that rcu_seq_done_exact() guardband doesn't give false positives. */ + WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && + rcu_seq_done_exact(&old_gp_seq, rcu_seq_snap(&rcu_state.gp_seq))); + ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq); trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start")); rcu_poll_gp_seq_start(&rcu_state.gp_seq_polled_snap); |