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Commit 252babcd authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
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tracing: Replace the per_cpu() with __this_cpu*() in trace_stack.c 



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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 0598e4f0

kernel/trace/trace_stack.c

+7 −16
Original line number Diff line number Diff line
@@ -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();

}