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| author |   Paul E. McKenney <paulmck@kernel.org> | 2020-06-23 17:09:27 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-08-24 18:36:06 -0700 |
| commit | b5374b2df0ac1c78895b8eb8d9582a7bdc67257d (patch) | |
| tree | fe85aaaab9d7064dbd619c4198537f9a5d727604 /kernel/rcu | |
| parent | nocb: Remove show_rcu_nocb_state() false positive printout (diff) | |
| download | linux-dev-b5374b2df0ac1c78895b8eb8d9582a7bdc67257d.tar.xz linux-dev-b5374b2df0ac1c78895b8eb8d9582a7bdc67257d.zip | |
rcu: Add READ_ONCE() to rcu_do_batch() access to rcu_divisor
Given that sysfs can change the value of rcu_divisor at any time, this
commit adds a READ_ONCE to the sole access to that variable. While in
the area, this commit also adds bounds checking, clamping the value to
a shift that makes sense for a signed long.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index acc926f07dc1..1dca14cf66f9 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2362,6 +2362,7 @@ int rcutree_dead_cpu(unsigned int cpu) */ static void rcu_do_batch(struct rcu_data *rdp) { + int div; unsigned long flags; const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) && rcu_segcblist_is_offloaded(&rdp->cblist); @@ -2390,7 +2391,9 @@ static void rcu_do_batch(struct rcu_data *rdp) rcu_nocb_lock(rdp); WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); pending = rcu_segcblist_n_cbs(&rdp->cblist); - bl = max(rdp->blimit, pending >> rcu_divisor); + div = READ_ONCE(rcu_divisor); + div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div; + bl = max(rdp->blimit, pending >> div); if (unlikely(bl > 100)) tlimit = local_clock() + rcu_resched_ns; trace_rcu_batch_start(rcu_state.name, |