linux-kernel - [PATCH tip/core/rcu 10/13] rcutorture: Add task's CPU for rcutorture writer stalls

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Message-Id: <1500935023-16620-10-git-send-email-paulmck@linux.vnet.ibm.com>
Date:   Mon, 24 Jul 2017 15:23:40 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 10/13] rcutorture: Add task's CPU for rcutorture writer stalls

It appears that at least some of the rcutorture writer stall messages
coincide with unusually long CPU-online operations, for example, no
fewer than 205 seconds in a recent test.  It is of course possible that
the writer stall is not unrelated to this unusually long CPU-hotplug
operation, and so this commit adds the rcutorture writer task's CPU to
the stall message to gain more information about this possible connection.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/rcutorture.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index b48d2107f176..75ac749ced7c 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1319,11 +1319,12 @@ rcu_torture_stats_print(void)
 		srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
 					&flags, &gpnum, &completed);
 		wtp = READ_ONCE(writer_task);
-		pr_alert("??? Writer stall state %s(%d) g%lu c%lu f%#x ->state %#lx\n",
+		pr_alert("??? Writer stall state %s(%d) g%lu c%lu f%#x ->state %#lx cpu %d\n",
 			 rcu_torture_writer_state_getname(),
 			 rcu_torture_writer_state,
 			 gpnum, completed, flags,
-			 wtp == NULL ? ~0UL : wtp->state);
+			 wtp == NULL ? ~0UL : wtp->state,
+			 wtp == NULL ? -1 : (int)task_cpu(wtp));
 		show_rcu_gp_kthreads();
 		rcu_ftrace_dump(DUMP_ALL);
 	}
-- 
2.5.2