From 79c6f448c8b79c321e4a1f31f98194e4f6b6cae7 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Mon, 30 Jan 2017 19:27:10 -0500 Subject: [PATCH] tracing: Fix hwlat kthread migration The hwlat tracer creates a kernel thread at start of the tracer. It is pinned to a single CPU and will move to the next CPU after each period of running. If the user modifies the migration thread's affinity, it will not change after that happens. The original code created the thread at the first instance it was called, but later was changed to destroy the thread after the tracer was finished, and would not be created until the next instance of the tracer was established. The code that initialized the affinity was only called on the initial instantiation of the tracer. After that, it was not initialized, and the previous affinity did not match the current newly created one, making it appear that the user modified the thread's affinity when it did not, and the thread failed to migrate again. Cc: stable@vger.kernel.org Fixes: 0330f7aa8ee6 ("tracing: Have hwlat trace migrate across tracing_cpumask CPUs") Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_hwlat.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c index 775569ec50d0..af344a1bf0d0 100644 --- a/kernel/trace/trace_hwlat.c +++ b/kernel/trace/trace_hwlat.c @@ -266,7 +266,7 @@ out: static struct cpumask save_cpumask; static bool disable_migrate; -static void move_to_next_cpu(void) +static void move_to_next_cpu(bool initmask) { static struct cpumask *current_mask; int next_cpu; @@ -275,7 +275,7 @@ static void move_to_next_cpu(void) return; /* Just pick the first CPU on first iteration */ - if (!current_mask) { + if (initmask) { current_mask = &save_cpumask; get_online_cpus(); cpumask_and(current_mask, cpu_online_mask, tracing_buffer_mask); @@ -330,10 +330,12 @@ static void move_to_next_cpu(void) static int kthread_fn(void *data) { u64 interval; + bool initmask = true; while (!kthread_should_stop()) { - move_to_next_cpu(); + move_to_next_cpu(initmask); + initmask = false; local_irq_disable(); get_sample(); -- 2.20.1