linux-kernel - [PATCH] powerpc/qspinlock: Add spinlock contention tracepoint

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Message-ID: <20250725081432.1254986-1-nysal@linux.ibm.com>
Date: Fri, 25 Jul 2025 13:44:29 +0530
From: "Nysal Jan K.A." <nysal@...ux.ibm.com>
To: Madhavan Srinivasan <maddy@...ux.ibm.com>
Cc: "Nysal Jan K.A." <nysal@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH] powerpc/qspinlock: Add spinlock contention tracepoint

Add a lock contention tracepoint in the queued spinlock slowpath.
Also add the __lockfunc annotation so that in_lock_functions()
works as expected.

Signed-off-by: Nysal Jan K.A. <nysal@...ux.ibm.com>
---
 arch/powerpc/lib/qspinlock.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/lib/qspinlock.c b/arch/powerpc/lib/qspinlock.c
index bcc7e4dff8c3..622e7f45c2ce 100644
--- a/arch/powerpc/lib/qspinlock.c
+++ b/arch/powerpc/lib/qspinlock.c
@@ -9,6 +9,7 @@
 #include <linux/sched/clock.h>
 #include <asm/qspinlock.h>
 #include <asm/paravirt.h>
+#include <trace/events/lock.h>
 
 #define MAX_NODES	4
 
@@ -708,8 +709,9 @@ static __always_inline void queued_spin_lock_mcs_queue(struct qspinlock *lock, b
 	qnodesp->count--;
 }
 
-void queued_spin_lock_slowpath(struct qspinlock *lock)
+void __lockfunc queued_spin_lock_slowpath(struct qspinlock *lock)
 {
+	trace_contention_begin(lock, LCB_F_SPIN);
 	/*
 	 * This looks funny, but it induces the compiler to inline both
 	 * sides of the branch rather than share code as when the condition
@@ -718,16 +720,17 @@ void queued_spin_lock_slowpath(struct qspinlock *lock)
 	if (IS_ENABLED(CONFIG_PARAVIRT_SPINLOCKS) && is_shared_processor()) {
 		if (try_to_steal_lock(lock, true)) {
 			spec_barrier();
-			return;
+		} else {
+			queued_spin_lock_mcs_queue(lock, true);
 		}
-		queued_spin_lock_mcs_queue(lock, true);
 	} else {
 		if (try_to_steal_lock(lock, false)) {
 			spec_barrier();
-			return;
+		} else {
+			queued_spin_lock_mcs_queue(lock, false);
 		}
-		queued_spin_lock_mcs_queue(lock, false);
 	}
+	trace_contention_end(lock, 0);
 }
 EXPORT_SYMBOL(queued_spin_lock_slowpath);
 
-- 
2.47.0