On 29/05/2019 10:41, Peter Zijlstra wrote:
> On Tue, May 28, 2019 at 05:16:24PM +0200, Daniel Bristot de Oliveira wrote:
>> #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
>> defined(CONFIG_TRACE_PREEMPT_TOGGLE))
>> +
>> +DEFINE_PER_CPU(int, __traced_preempt_count) = 0;
>> /*
>> * If the value passed in is equal to the current preempt count
>> * then we just disabled preemption. Start timing the latency.
>> */
>> void preempt_latency_start(int val)
>> {
>> - if (preempt_count() == val) {
>> + int curr = this_cpu_read(__traced_preempt_count);
>
> We actually have this_cpu_add_return();
>
>> +
>> + if (!curr) {
>> unsigned long ip = get_lock_parent_ip();
>> #ifdef CONFIG_DEBUG_PREEMPT
>> current->preempt_disable_ip = ip;
>> #endif
>> trace_preempt_off(CALLER_ADDR0, ip);
>> }
>> +
>> + this_cpu_write(__traced_preempt_count, curr + val);
>> }
>>
>> static inline void preempt_add_start_latency(int val)
>> @@ -3200,8 +3206,12 @@ NOKPROBE_SYMBOL(preempt_count_add);
>> */
>> void preempt_latency_stop(int val)
>> {
>> - if (preempt_count() == val)
>> + int curr = this_cpu_read(__traced_preempt_count) - val;
>
> this_cpu_sub_return();
>
>> +
>> + if (!curr)
>> trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
>> +
>> + this_cpu_write(__traced_preempt_count, curr);
>> }
>
> Can't say I love this, but it is miles better than the last patch.
>
ack! I will change the methods (and remove some blank lines here and there...
:-))
Thanks Peter!
-- Daniel
