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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2016-11-29 05:49:06 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-01-23 11:37:12 -0800 |
| commit | 7aa92230c9e86b2150f718185f70e0af592e290b (patch) | |
| tree | a0402e24bc7048f590a7bffce9953845dfdc5fb9 /kernel/rcu/tree.c | |
| parent | b201fa67371862229f27a1f022196423aa5c7381 (diff) | |
| download | lwn-7aa92230c9e86b2150f718185f70e0af592e290b.tar.gz lwn-7aa92230c9e86b2150f718185f70e0af592e290b.zip | |
rcu: Once again use NMI-based stack traces in stall warnings
This commit is for all intents and purposes a revert of bc1dce514e9b
("rcu: Don't use NMIs to dump other CPUs' stacks"). The reason to suppose
that this can now safely be reverted is the presence of 42a0bb3f7138
("printk/nmi: generic solution for safe printk in NMI"), which is said
to have made NMI-based stack dumps safe.
However, this reversion keeps one nice property of bc1dce514e9b
("rcu: Don't use NMIs to dump other CPUs' stacks"), namely that
only those CPUs blocking the grace period are dumped. The new
trigger_single_cpu_backtrace() is used to make this happen, as
suggested by Josh Poimboeuf.
Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/rcu/tree.c')
| -rw-r--r-- | kernel/rcu/tree.c | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 5a4aaad75e76..d7b63b88434b 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1278,7 +1278,10 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp) } /* - * Dump stacks of all tasks running on stalled CPUs. + * Dump stacks of all tasks running on stalled CPUs. First try using + * NMIs, but fall back to manual remote stack tracing on architectures + * that don't support NMI-based stack dumps. The NMI-triggered stack + * traces are more accurate because they are printed by the target CPU. */ static void rcu_dump_cpu_stacks(struct rcu_state *rsp) { @@ -1288,11 +1291,10 @@ static void rcu_dump_cpu_stacks(struct rcu_state *rsp) rcu_for_each_leaf_node(rsp, rnp) { raw_spin_lock_irqsave_rcu_node(rnp, flags); - if (rnp->qsmask != 0) { - for_each_leaf_node_possible_cpu(rnp, cpu) - if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) + for_each_leaf_node_possible_cpu(rnp, cpu) + if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) + if (!trigger_single_cpu_backtrace(cpu)) dump_cpu_task(cpu); - } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } } |