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author | Paul E. McKenney <paulmck@kernel.org> | 2019-08-02 15:12:47 -0700 |
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committer | Paul E. McKenney <paulmck@kernel.org> | 2019-10-05 10:46:05 -0700 |
commit | 96926686deab853bcacf887501f4ed958e38666b (patch) | |
tree | 197e4fb14f6edaa8fae310e415f4d981905457b1 /kernel/rcu/tree.c | |
parent | 366237e7b0833faa2d8da7a8d7d7da8c3ca802e5 (diff) | |
download | linux-96926686deab853bcacf887501f4ed958e38666b.tar.bz2 |
rcu: Make CPU-hotplug removal operations enable tick
CPU-hotplug removal operations run the multi_cpu_stop() function, which
relies on the scheduler to gain control from whatever is running on the
various online CPUs, including any nohz_full CPUs running long loops in
kernel-mode code. Lack of the scheduler-clock interrupt on such CPUs
can delay multi_cpu_stop() for several minutes and can also result in
RCU CPU stall warnings. This commit therefore causes CPU-hotplug removal
operations to enable the scheduler-clock interrupt on all online CPUs.
[ paulmck: Apply Joel Fernandes TICK_DEP_MASK_RCU->TICK_DEP_BIT_RCU fix. ]
[ paulmck: Apply simplifications suggested by Frederic Weisbecker. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu/tree.c')
-rw-r--r-- | kernel/rcu/tree.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index a5c296d202ae..7c67ea561b36 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2101,6 +2101,9 @@ int rcutree_dead_cpu(unsigned int cpu) rcu_boost_kthread_setaffinity(rnp, -1); /* Do any needed no-CB deferred wakeups from this CPU. */ do_nocb_deferred_wakeup(per_cpu_ptr(&rcu_data, cpu)); + + // Stop-machine done, so allow nohz_full to disable tick. + tick_dep_clear(TICK_DEP_BIT_RCU); return 0; } @@ -3085,6 +3088,9 @@ int rcutree_online_cpu(unsigned int cpu) return 0; /* Too early in boot for scheduler work. */ sync_sched_exp_online_cleanup(cpu); rcutree_affinity_setting(cpu, -1); + + // Stop-machine done, so allow nohz_full to disable tick. + tick_dep_clear(TICK_DEP_BIT_RCU); return 0; } @@ -3105,6 +3111,9 @@ int rcutree_offline_cpu(unsigned int cpu) raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcutree_affinity_setting(cpu, cpu); + + // nohz_full CPUs need the tick for stop-machine to work quickly + tick_dep_set(TICK_DEP_BIT_RCU); return 0; } |