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| author | Frederic Weisbecker <frederic@kernel.org> | 2021-02-23 01:10:06 +0100 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2021-05-12 12:10:23 -0700 |
| commit | 552cac80e65f38a0cc9022456c09efed7e88f9d6 (patch) | |
| tree | 890b0f0c5d4000befd314abf34829fd7d28877e5 /kernel/rcu | |
| parent | c7ef7500a891432a3bb2b036f535bfdf58aa3605 (diff) | |
| download | lwn-552cac80e65f38a0cc9022456c09efed7e88f9d6.tar.gz lwn-552cac80e65f38a0cc9022456c09efed7e88f9d6.zip | |
rcu/nocb: Allow de-offloading rdp leader
The only thing that prevented an rdp leader from being de-offloaded was
the nocb_bypass_timer that used to lock the nocb_lock of the rdp leader.
If an rdp gets de-offloaded, it will subtlely ignore rcu_nocb_lock()
calls and do its job in the timer unsafely. Worse yet: If it gets
re-offloaded in the middle of the timer, rcu_nocb_unlock() would try to
unlock, leaving it imbalanced.
Now that the nocb_bypass_timer doesn't use the nocb_lock anymore,
de-offloading the rdp leader is now safe. This commit therefore allows
the rdp leader to be de-offloaded.
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 4 |
1 files changed, 0 insertions, 4 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 82e9ffb92347..015adec5bdc5 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2489,10 +2489,6 @@ int rcu_nocb_cpu_deoffload(int cpu) struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); int ret = 0; - if (rdp == rdp->nocb_gp_rdp) { - pr_info("Can't deoffload an rdp GP leader (yet)\n"); - return -EINVAL; - } mutex_lock(&rcu_state.barrier_mutex); cpus_read_lock(); if (rcu_rdp_is_offloaded(rdp)) { |