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rcu: Detect stalls caused by failure to propagate up rcu_node tree

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If all CPUs have passed through quiescent states, then stalls might be
due to starvation of the grace-period kthread or to failure to propagate
the quiescent states up the rcu_node combining tree.  The current stall
warning messages do not differentiate, so this commit adds a printout
of the root rcu_node structure's ->qsmask field.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2015-01-22 14:32:06 -08:00
parent 18c629eaeb
commit 237a0f2193
1 changed files with 3 additions and 2 deletions
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5
kernel/rcu/tree.c
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@ -1196,9 +1196,10 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
} else { } else {
j = jiffies; j = jiffies;
gpa = ACCESS_ONCE(rsp->gp_activity); gpa = ACCESS_ONCE(rsp->gp_activity);
pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld\n", pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n",
rsp->name, j - gpa, j, gpa, rsp->name, j - gpa, j, gpa,
jiffies_till_next_fqs); jiffies_till_next_fqs,
rcu_get_root(rsp)->qsmask);
/* In this case, the current CPU might be at fault. */ /* In this case, the current CPU might be at fault. */
sched_show_task(current); sched_show_task(current);
} }