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tracing: Replace the per_cpu() with __this_cpu*() in trace_stack.c

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The updates to the trace_active per cpu variable can be updated with the
__this_cpu_*() functions as it only gets updated on the CPU that the variable
is on.

Thanks to Paul McKenney for suggesting __this_cpu_* instead of this_cpu_*.

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2017-04-06 12:11:36 -04:00
parent 0598e4f08e
commit 252babcd52
1 changed files with 7 additions and 16 deletions
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23
kernel/trace/trace_stack.c
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@ -207,13 +207,12 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct pt_regs *pt_regs)
{
unsigned long stack;
int cpu;
preempt_disable_notrace();
cpu = raw_smp_processor_id();
/* no atomic needed, we only modify this variable by this cpu */
if (per_cpu(trace_active, cpu)++ != 0)
__this_cpu_inc(trace_active);
if (__this_cpu_read(trace_active) != 1)
goto out;
ip += MCOUNT_INSN_SIZE;
@ -221,7 +220,7 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip,
check_stack(ip, &stack);
out:
per_cpu(trace_active, cpu)--;
__this_cpu_dec(trace_active);
/* prevent recursion in schedule */
preempt_enable_notrace();
}
@ -253,7 +252,6 @@ stack_max_size_write(struct file *filp, const char __user *ubuf,
long *ptr = filp->private_data;
unsigned long val, flags;
int ret;
int cpu;
ret = kstrtoul_from_user(ubuf, count, 10, &val);
if (ret)
@ -266,14 +264,13 @@ stack_max_size_write(struct file *filp, const char __user *ubuf,
* we will cause circular lock, so we also need to increase
* the percpu trace_active here.
*/
cpu = smp_processor_id();
per_cpu(trace_active, cpu)++;
__this_cpu_inc(trace_active);
arch_spin_lock(&stack_trace_max_lock);
*ptr = val;
arch_spin_unlock(&stack_trace_max_lock);
per_cpu(trace_active, cpu)--;
__this_cpu_dec(trace_active);
local_irq_restore(flags);
return count;
@ -307,12 +304,9 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
static void *t_start(struct seq_file *m, loff_t *pos)
{
int cpu;
local_irq_disable();
cpu = smp_processor_id();
per_cpu(trace_active, cpu)++;
__this_cpu_inc(trace_active);
arch_spin_lock(&stack_trace_max_lock);
@ -324,12 +318,9 @@ static void *t_start(struct seq_file *m, loff_t *pos)
static void t_stop(struct seq_file *m, void *p)
{
int cpu;
arch_spin_unlock(&stack_trace_max_lock);
cpu = smp_processor_id();
per_cpu(trace_active, cpu)--;
__this_cpu_dec(trace_active);
local_irq_enable();
}