[v2,14/27] context_tracking, rcu: Rename rcu_dynticks_curr_cpu_in_eqs() into rcu_watching_curr_cpu()

Commit Message

Valentin Schneider April 30, 2024, 9:17 a.m. UTC

The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, reflect that change in the related helpers.

Note that "watching" is the opposite of "in EQS", so the negation is lifted
out of the helper and into the callsites.

Signed-off-by: Valentin Schneider <[e-mail]>
---
 include/linux/context_tracking.h | 12 ++++++++----
 kernel/context_tracking.c        |  6 +++---
 kernel/rcu/tree.c                |  6 +++---
 3 files changed, 14 insertions(+), 10 deletions(-)

Comments

Frederic Weisbecker May 6, 2024, 10 p.m. UTC | #1

Le Tue, Apr 30, 2024 at 11:17:18AM +0200, Valentin Schneider a écrit :
> The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
> RCU_WATCHING, reflect that change in the related helpers.
> 
> Note that "watching" is the opposite of "in EQS", so the negation is lifted
> out of the helper and into the callsites.
> 
> Signed-off-by: Valentin Schneider <[e-mail]>

Reviewed-by: Frederic Weisbecker <[e-mail]>

Patch

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index a6c36780cc3bd..d53092ffa9dba 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -113,13 +113,17 @@  extern void ct_idle_enter(void);
 extern void ct_idle_exit(void);
 
 /*
- * Is the current CPU in an extended quiescent state?
+ * Is RCU watching the current CPU (IOW, it is not in an extended quiescent state)?
+ *
+ * Note that this returns the actual boolean data (watching / not watching),
+ * whereas ct_rcu_watching() returns the RCU_WATCHING subvariable of
+ * context_tracking.state.
  *
  * No ordering, as we are sampling CPU-local information.
  */
-static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void)
+static __always_inline bool rcu_is_watching_curr_cpu(void)
 {
-	return !(raw_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_RCU_WATCHING);
+	return raw_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_RCU_WATCHING;
 }
 
 /*
@@ -140,7 +144,7 @@  static __always_inline bool warn_rcu_enter(void)
 	 * lots of the actual reporting also relies on RCU.
 	 */
 	preempt_disable_notrace();
-	if (rcu_dynticks_curr_cpu_in_eqs()) {
+	if (!rcu_is_watching_curr_cpu()) {
 		ret = true;
 		ct_state_inc(CT_RCU_WATCHING);
 	}
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 9c8f7b9191cd4..e82f19bab9ed9 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -212,7 +212,7 @@  void noinstr ct_nmi_exit(void)
 	 * to us!)
 	 */
 	WARN_ON_ONCE(ct_nmi_nesting() <= 0);
-	WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
+	WARN_ON_ONCE(!rcu_is_watching_curr_cpu());
 
 	/*
 	 * If the nesting level is not 1, the CPU wasn't RCU-idle, so
@@ -271,7 +271,7 @@  void noinstr ct_nmi_enter(void)
 	 * to be in the outermost NMI handler that interrupted an RCU-idle
 	 * period (observation due to Andy Lutomirski).
 	 */
-	if (rcu_dynticks_curr_cpu_in_eqs()) {
+	if (!rcu_is_watching_curr_cpu()) {
 
 		if (!in_nmi())
 			rcu_task_exit();
@@ -281,7 +281,7 @@  void noinstr ct_nmi_enter(void)
 		// ... but is watching here.
 
 		instrumentation_begin();
-		// instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs()
+		// instrumentation for the noinstr rcu_is_watching_curr_cpu()
 		instrument_atomic_read(&ct->state, sizeof(ct->state));
 		// instrumentation for the noinstr ct_kernel_enter_state()
 		instrument_atomic_write(&ct->state, sizeof(ct->state));
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index d8f89bc573448..bb0d9dd8b6d3a 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -600,7 +600,7 @@  void rcu_irq_exit_check_preempt(void)
 	RCU_LOCKDEP_WARN(ct_nmi_nesting() !=
 			 CT_NESTING_IRQ_NONIDLE,
 			 "Bad RCU  nmi_nesting counter\n");
-	RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
+	RCU_LOCKDEP_WARN(!rcu_is_watching_curr_cpu(),
 			 "RCU in extended quiescent state!");
 }
 #endif /* #ifdef CONFIG_PROVE_RCU */
@@ -640,7 +640,7 @@  void __rcu_irq_enter_check_tick(void)
 	if (in_nmi())
 		return;
 
-	RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
+	RCU_LOCKDEP_WARN(!rcu_is_watching_curr_cpu(),
 			 "Illegal rcu_irq_enter_check_tick() from extended quiescent state");
 
 	if (!tick_nohz_full_cpu(rdp->cpu) ||
@@ -722,7 +722,7 @@  notrace bool rcu_is_watching(void)
 	bool ret;
 
 	preempt_disable_notrace();
-	ret = !rcu_dynticks_curr_cpu_in_eqs();
+	ret = rcu_is_watching_curr_cpu();
 	preempt_enable_notrace();
 	return ret;
 }