Commit-ID: ec1fe396ff42e240c9b32111ee53665c5916fe5e
Gitweb: http://git.kernel.org/tip/ec1fe396ff42e240c9b32111ee53665c5916fe5e
Author: Miroslav Benes <mbenes@xxxxxxx>
AuthorDate: Mon, 22 Dec 2014 11:10:12 -0800
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 15 Jan 2015 23:33:16 -0800
rcu: Fix RCU CPU stall detection in tiny implementation
The tiny RCU CPU stall detection depends on *rcp->curtail not being
NULL. It is however a tail pointer and thus NULL by definition. Instead we
should check rcp->rcucblist for the presence of pending callbacks which
need to be processed. With this fix INFO about the stall is printed and
jiffies_stall (jiffies at next stall) correctly updated.
Note that the check for pending callback is necessary to avoid spurious
warnings if there are no pendings callbacks.
Signed-off-by: Miroslav Benes <mbenes@xxxxxxx>
[ paulmck: Fused identical "if" statements, ported to -rcu. ]
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tiny_plugin.h | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/kernel/rcu/tiny_plugin.h b/kernel/rcu/tiny_plugin.h
index 858c565..80f908a 100644
--- a/kernel/rcu/tiny_plugin.h
+++ b/kernel/rcu/tiny_plugin.h
@@ -145,17 +145,16 @@ static void check_cpu_stall(struct rcu_ctrlblk *rcp)
rcp->ticks_this_gp++;
j = jiffies;
js = ACCESS_ONCE(rcp->jiffies_stall);
- if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
+ if (rcp->rcucblist && ULONG_CMP_GE(j, js)) {
pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
jiffies - rcp->gp_start, rcp->qlen);
dump_stack();
- }
- if (*rcp->curtail && ULONG_CMP_GE(j, js))
ACCESS_ONCE(rcp->jiffies_stall) = jiffies +
3 * rcu_jiffies_till_stall_check() + 3;
- else if (ULONG_CMP_GE(j, js))
+ } else if (ULONG_CMP_GE(j, js)) {
ACCESS_ONCE(rcp->jiffies_stall) = jiffies + rcu_jiffies_till_stall_check();
+ }
}
static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
--
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