ftrace: make use of tracing_cpumask

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 64 insertions, 31 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 18f0ab88ca85..3ae17e254fc3 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -70,23 +70,6 @@ static DECLARE_WAIT_QUEUE_HEAD(trace_wait);
 
 unsigned long trace_flags = TRACE_ITER_PRINT_PARENT;
 
-/*
- * Only trace on a CPU if the bitmask is set:
- */
-static cpumask_t tracing_cpumask __read_mostly = CPU_MASK_ALL;
-
-/*
- * The tracer itself will not take this lock, but still we want
- * to provide a consistent cpumask to user-space:
- */
-static DEFINE_MUTEX(tracing_cpumask_update_lock);
-
-/*
- * Temporary storage for the character representation of the
- * CPU bitmask:
- */
-static char mask_str[NR_CPUS];
-
 void trace_wake_up(void)
 {
         /*
@@ -1776,19 +1759,46 @@ static struct file_operations show_traces_fops = {
         .release        = seq_release,
 };
 
+/*
+ * Only trace on a CPU if the bitmask is set:
+ */
+static cpumask_t tracing_cpumask = CPU_MASK_ALL;
+
+/*
+ * When tracing/tracing_cpu_mask is modified then this holds
+ * the new bitmask we are about to install:
+ */
+static cpumask_t tracing_cpumask_new;
+
+/*
+ * The tracer itself will not take this lock, but still we want
+ * to provide a consistent cpumask to user-space:
+ */
+static DEFINE_MUTEX(tracing_cpumask_update_lock);
+
+/*
+ * Temporary storage for the character representation of the
+ * CPU bitmask (and one more byte for the newline):
+ */
+static char mask_str[NR_CPUS + 1];
+
 static ssize_t
 tracing_cpumask_read(struct file *filp, char __user *ubuf,
                      size_t count, loff_t *ppos)
 {
-        int err;
-
-        count = min(count, (size_t)NR_CPUS);
+        int len;
 
         mutex_lock(&tracing_cpumask_update_lock);
-        cpumask_scnprintf(mask_str, NR_CPUS, tracing_cpumask);
-        err = copy_to_user(ubuf, mask_str, count);
-        if (err)
-                count = -EFAULT;
+
+        len = cpumask_scnprintf(mask_str, count, tracing_cpumask);
+        if (count - len < 2) {
+                count = -EINVAL;
+                goto out_err;
+        }
+        len += sprintf(mask_str + len, "\n");
+        count = simple_read_from_buffer(ubuf, count, ppos, mask_str, NR_CPUS+1);
+
+out_err:
         mutex_unlock(&tracing_cpumask_update_lock);
 
         return count;
@@ -1798,16 +1808,40 @@ static ssize_t
 tracing_cpumask_write(struct file *filp, const char __user *ubuf,
                       size_t count, loff_t *ppos)
 {
-        int err;
+        int err, cpu;
 
         mutex_lock(&tracing_cpumask_update_lock);
-        err = cpumask_parse_user(ubuf, count, tracing_cpumask);
-        mutex_unlock(&tracing_cpumask_update_lock);
-
+        err = cpumask_parse_user(ubuf, count, tracing_cpumask_new);
         if (err)
-                return err;
+                goto err_unlock;
+
+        spin_lock_irq(&ftrace_max_lock);
+        for_each_possible_cpu(cpu) {
+                /*
+                 * Increase/decrease the disabled counter if we are
+                 * about to flip a bit in the cpumask:
+                 */
+                if (cpu_isset(cpu, tracing_cpumask) &&
+                                !cpu_isset(cpu, tracing_cpumask_new)) {
+                        atomic_inc(&global_trace.data[cpu]->disabled);
+                }
+                if (!cpu_isset(cpu, tracing_cpumask) &&
+                                cpu_isset(cpu, tracing_cpumask_new)) {
+                        atomic_dec(&global_trace.data[cpu]->disabled);
+                }
+        }
+        spin_unlock_irq(&ftrace_max_lock);
+
+        tracing_cpumask = tracing_cpumask_new;
+
+        mutex_unlock(&tracing_cpumask_update_lock);
 
         return count;
+
+err_unlock:
+        mutex_unlock(&tracing_cpumask_update_lock);
+
+        return err;
 }
 
 static struct file_operations tracing_cpumask_fops = {
@@ -1846,8 +1880,7 @@ tracing_iter_ctrl_read(struct file *filp, char __user *ubuf,
         r += sprintf(buf + r, "\n");
         WARN_ON(r >= len + 2);
 
-        r = simple_read_from_buffer(ubuf, cnt, ppos,
-                                    buf, r);
+        r = simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
 
         kfree(buf);