[RFC,4/5] irq_work: Trace calls to arch_irq_work_raise()

Commit Message

Valentin Schneider Oct. 7, 2022, 3:45 p.m. UTC

Adding a tracepoint to send_call_function_single_ipi() covers
irq_work_queue_on() when the CPU isn't the local one - add a tracepoint to
irq_work_raise() to cover the other cases.

Signed-off-by: Valentin Schneider <[e-mail]>
---
 kernel/irq_work.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Comments

Steven Rostedt Oct. 8, 2022, 7:34 p.m. UTC | #1

On Fri,  7 Oct 2022 16:45:32 +0100
Valentin Schneider <[e-mail]> wrote:
>  }
>  
> +static inline void irq_work_raise(void)
> +{
> +	if (arch_irq_work_has_interrupt())
> +		trace_ipi_send_cpu(_RET_IP_, smp_processor_id());

To save on the branch, let's make the above:

	if (trace_ipi_send_cpu_enabled() && arch_irq_work_has_interrupt())

As the "trace_*_enabled()" is a static branch that will make it a nop
when the tracepoint is not enabled.

-- Steve


> +
> +	arch_irq_work_raise();
> +}
> +
>  /* Enqueue on current CPU, work must already be claimed and preempt disabled */

Valentin Schneider Oct. 11, 2022, 3:02 p.m. UTC | #2

On 08/10/22 15:34, Steven Rostedt wrote:
> On Fri,  7 Oct 2022 16:45:32 +0100
> Valentin Schneider <[e-mail]> wrote:
>>  }
>>  
>> +static inline void irq_work_raise(void)
>> +{
>> +	if (arch_irq_work_has_interrupt())
>> +		trace_ipi_send_cpu(_RET_IP_, smp_processor_id());
>
> To save on the branch, let's make the above:
>
> 	if (trace_ipi_send_cpu_enabled() && arch_irq_work_has_interrupt())
>
> As the "trace_*_enabled()" is a static branch that will make it a nop
> when the tracepoint is not enabled.
>

Makes sense, thanks for the suggestion.

> -- Steve
>
>
>> +
>> +	arch_irq_work_raise();
>> +}
>> +
>>  /* Enqueue on current CPU, work must already be claimed and preempt disabled */

Patch

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 7afa40fe5cc4..5a550b681878 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -22,6 +22,8 @@ 
 #include <asm/processor.h>
 #include <linux/kasan.h>
 
+#include <trace/events/ipi.h>
+
 static DEFINE_PER_CPU(struct llist_head, raised_list);
 static DEFINE_PER_CPU(struct llist_head, lazy_list);
 static DEFINE_PER_CPU(struct task_struct *, irq_workd);
@@ -74,6 +76,14 @@  void __weak arch_irq_work_raise(void)
 	 */
 }
 
+static inline void irq_work_raise(void)
+{
+	if (arch_irq_work_has_interrupt())
+		trace_ipi_send_cpu(_RET_IP_, smp_processor_id());
+
+	arch_irq_work_raise();
+}
+
 /* Enqueue on current CPU, work must already be claimed and preempt disabled */
 static void __irq_work_queue_local(struct irq_work *work)
 {
@@ -99,7 +109,7 @@  static void __irq_work_queue_local(struct irq_work *work)
 
 	/* If the work is "lazy", handle it from next tick if any */
 	if (!lazy_work || tick_nohz_tick_stopped())
-		arch_irq_work_raise();
+		irq_work_raise();
 }
 
 /* Enqueue the irq work @work on the current CPU */