linux-kernel - [PATCH tip/core/rcu 11/15] rcu: Add more debug info on "kthread starved" RCU CPU stall warnings

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Message-Id: <1431466701-653-11-git-send-email-paulmck@linux.vnet.ibm.com>
Date:	Tue, 12 May 2015 14:38:17 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, laijs@...fujitsu.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,
	dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
	bobby.prani@...il.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 11/15] rcu: Add more debug info on "kthread starved" RCU CPU stall warnings

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

This commit adds grace number and command-flags information to the
"kthread starved" message that is sometimes printed out as part of
RCU CPU stall warnings.  This message is caused by the corresponding
RCU grace-period kthread not having run for at least two seconds, and
this added information can be helpful when debugging.

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

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a7615a0b684f..5b573e75e0f8 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1133,8 +1133,9 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
 	j = jiffies;
 	gpa = READ_ONCE(rsp->gp_activity);
 	if (j - gpa > 2 * HZ)
-		pr_err("%s kthread starved for %ld jiffies!\n",
-		       rsp->name, j - gpa);
+		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x\n",
+		       rsp->name, j - gpa,
+		       rsp->gpnum, rsp->completed, rsp->gp_flags);
 }
 
 /*
-- 
1.8.1.5

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