diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2020-01-03 11:42:05 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-02-20 16:01:11 -0800 |
| commit | 710426068dc60f2d2e139478d6185710802cdc0a (patch) | |
| tree | 00005fee34c298dea42e655f5e06a42392cba95d /kernel/rcu | |
| parent | 39f91504a03a7a2abdb52205106942fa4a548d0d (diff) | |
srcu: Hold srcu_struct ->lock when updating ->srcu_gp_seq
A read of the srcu_struct structure's ->srcu_gp_seq field should not
need READ_ONCE() when that structure's ->lock is held. Except that this
lock is not always held when updating this field. This commit therefore
acquires the lock around updates and removes a now-unneeded READ_ONCE().
This data race was reported by KCSAN.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
[ paulmck: Switch from READ_ONCE() to lock per Peter Zilstra question. ]
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/srcutree.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 119a37319e67..c19c1df0d198 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -450,7 +450,7 @@ static void srcu_gp_start(struct srcu_struct *ssp) spin_unlock_rcu_node(sdp); /* Interrupts remain disabled. */ smp_mb(); /* Order prior store to ->srcu_gp_seq_needed vs. GP start. */ rcu_seq_start(&ssp->srcu_gp_seq); - state = rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)); + state = rcu_seq_state(ssp->srcu_gp_seq); WARN_ON_ONCE(state != SRCU_STATE_SCAN1); } @@ -1130,7 +1130,9 @@ static void srcu_advance_state(struct srcu_struct *ssp) return; /* readers present, retry later. */ } srcu_flip(ssp); + spin_lock_irq_rcu_node(ssp); rcu_seq_set_state(&ssp->srcu_gp_seq, SRCU_STATE_SCAN2); + spin_unlock_irq_rcu_node(ssp); } if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_SCAN2) { |