[PATCH 4.9 05/39] tracing: Clean up the hwlat binding code

Greg Kroah-Hartman
2020-08-24T08:52:32Z

From: Steven Rostedt (VMware) <rostedt@goodmis.org>

[ Upstream commit f447c196fe7a3a92c6396f7628020cb8d564be15 ]

Instead of initializing the affinity of the hwlat kthread in the thread
itself, simply set up the initial affinity at thread creation. This
simplifies the code.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/trace/trace_hwlat.c | 34 +++++++++++++++++-----------------
1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index 5fe23f0ee7db6..158af5ddbc3aa 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -268,24 +268,13 @@ out:
static struct cpumask save_cpumask;
static bool disable_migrate;

-static void move_to_next_cpu(bool initmask)
+static void move_to_next_cpu(void)
{
- static struct cpumask *current_mask;
+ struct cpumask *current_mask = &save_cpumask;
int next_cpu;

if (disable_migrate)
return;
-
- /* Just pick the first CPU on first iteration */
- if (initmask) {
- current_mask = &save_cpumask;
- get_online_cpus();
- cpumask_and(current_mask, cpu_online_mask, tracing_buffer_mask);
- put_online_cpus();
- next_cpu = cpumask_first(current_mask);
- goto set_affinity;
- }
-
/*
* If for some reason the user modifies the CPU affinity
* of this thread, than stop migrating for the duration
@@ -302,7 +291,6 @@ static void move_to_next_cpu(bool initmask)
if (next_cpu >= nr_cpu_ids)
next_cpu = cpumask_first(current_mask);

- set_affinity:
if (next_cpu >= nr_cpu_ids) /* Shouldn't happen! */
goto disable;

@@ -332,12 +320,10 @@ static void move_to_next_cpu(bool initmask)
static int kthread_fn(void *data)
{
u64 interval;
- bool initmask = true;

while (!kthread_should_stop()) {

- move_to_next_cpu(initmask);
- initmask = false;
+ move_to_next_cpu();

local_irq_disable();
get_sample();
@@ -368,13 +354,27 @@ static int kthread_fn(void *data)
*/
static int start_kthread(struct trace_array *tr)
{
+ struct cpumask *current_mask = &save_cpumask;
struct task_struct *kthread;
+ int next_cpu;
+
+ /* Just pick the first CPU on first iteration */
+ current_mask = &save_cpumask;
+ get_online_cpus();
+ cpumask_and(current_mask, cpu_online_mask, tracing_buffer_mask);
+ put_online_cpus();
+ next_cpu = cpumask_first(current_mask);

kthread = kthread_create(kthread_fn, NULL, "hwlatd");
if (IS_ERR(kthread)) {
pr_err(BANNER "could not start sampling thread\n");
return -ENOMEM;
}
+
+ cpumask_clear(current_mask);
+ cpumask_set_cpu(next_cpu, current_mask);
+ sched_setaffinity(kthread->pid, current_mask);
+
hwlat_kthread = kthread;
wake_up_process(kthread);

--
2.25.1