[firefly] [PATCH] rcu: Notice if an all-zero cpumask is set inside a critical section

Iulia Manda iulia.manda21 at gmail.com
Mon Mar 17 13:53:01 EET 2014

In torture_shuffle_tasks function, the check if an all-zero mask can
be passed to set_cpus_allowed_ptr() is redundant after clearing the
shuffle_idle_cpu bit. If the mask had more than one bit set, after
clearing a bit it has at least one bit set. If the mask had only
one bit set, a check is made at the beginning, where the function
returns, as there is no need to shuffle only one cpu.

Also, this code is executed inside a critical section, delimited by
get_online_cpus() and put_online_cpus(), preventing CPUs from leaving between
the check of num_online_cpus and the calls to set_cpus_allowed_ptr().

Signed-off-by: Iulia Manda <iulia.manda21 at gmail.com>
 kernel/torture.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/kernel/torture.c b/kernel/torture.c
index 5ee9af4..25c87b5 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -341,13 +341,8 @@ static void torture_shuffle_tasks(void)
 	shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
 	if (shuffle_idle_cpu >= nr_cpu_ids)
 		shuffle_idle_cpu = -1;
-	if (shuffle_idle_cpu != -1) {
+	else
 		cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
-		if (cpumask_empty(shuffle_tmp_mask)) {
-			put_online_cpus();
-			return;
-		}
-	}
 	list_for_each_entry(stp, &shuffle_task_list, st_l)

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