Merge tag 'smp-core-2023-04-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull SMP cross-CPU function-call updates from Ingo Molnar:

 - Remove diagnostics and adjust config for CSD lock diagnostics

 - Add a generic IPI-sending tracepoint, as currently there's no easy
   way to instrument IPI origins: it's arch dependent and for some major
   architectures it's not even consistently available.

* tag 'smp-core-2023-04-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  trace,smp: Trace all smp_function_call*() invocations
  trace: Add trace_ipi_send_cpu()
  sched, smp: Trace smp callback causing an IPI
  smp: reword smp call IPI comment
  treewide: Trace IPIs sent via smp_send_reschedule()
  irq_work: Trace self-IPIs sent via arch_irq_work_raise()
  smp: Trace IPIs sent via arch_send_call_function_ipi_mask()
  sched, smp: Trace IPIs sent via send_call_function_single_ipi()
  trace: Add trace_ipi_send_cpumask()
  kernel/smp: Make csdlock_debug= resettable
  locking/csd_lock: Remove per-CPU data indirection from CSD lock debugging
  locking/csd_lock: Remove added data from CSD lock debugging
  locking/csd_lock: Add Kconfig option for csd_debug default

2 files changed, 17 insertions, 7 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 54c75af24899..944c3ae39861 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -80,6 +80,7 @@
 #define CREATE_TRACE_POINTS
 #include <linux/sched/rseq_api.h>
 #include <trace/events/sched.h>
+#include <trace/events/ipi.h>
 #undef CREATE_TRACE_POINTS
 
 #include "sched.h"
@@ -95,6 +96,9 @@
 #include "../../io_uring/io-wq.h"
 #include "../smpboot.h"
 
+EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpu);
+EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpumask);
+
 /*
  * Export tracepoints that act as a bare tracehook (ie: have no trace event
  * associated with them) to allow external modules to probe them.
@@ -3848,14 +3852,20 @@ void sched_ttwu_pending(void *arg)
 	rq_unlock_irqrestore(rq, &rf);
 }
 
-void send_call_function_single_ipi(int cpu)
+/*
+ * Prepare the scene for sending an IPI for a remote smp_call
+ *
+ * Returns true if the caller can proceed with sending the IPI.
+ * Returns false otherwise.
+ */
+bool call_function_single_prep_ipi(int cpu)
 {
-	struct rq *rq = cpu_rq(cpu);
-
-	if (!set_nr_if_polling(rq->idle))
-		arch_send_call_function_single_ipi(cpu);
-	else
+	if (set_nr_if_polling(cpu_rq(cpu)->idle)) {
 		trace_sched_wake_idle_without_ipi(cpu);
+		return false;
+	}
+
+	return true;
 }
 
 /*
diff --git a/kernel/sched/smp.h b/kernel/sched/smp.h
index 2eb23dd0f285..21ac44428bb0 100644
--- a/kernel/sched/smp.h
+++ b/kernel/sched/smp.h
@@ -6,7 +6,7 @@
 
 extern void sched_ttwu_pending(void *arg);
 
-extern void send_call_function_single_ipi(int cpu);
+extern bool call_function_single_prep_ipi(int cpu);
 
 #ifdef CONFIG_SMP
 extern void flush_smp_call_function_queue(void);