linux-kernel - [PATCH rcu 08/17] srcu: Rename srcu_check_read_flavor_lite() to srcu_check_read_flavor

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Message-Id: <20250116202112.3783327-8-paulmck@kernel.org>
Date: Thu, 16 Jan 2025 12:21:03 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	kernel-team@...a.com,
	rostedt@...dmis.org,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	bpf@...r.kernel.org
Subject: [PATCH rcu 08/17] srcu: Rename srcu_check_read_flavor_lite() to srcu_check_read_flavor_force()

This commit renames the srcu_check_read_flavor_lite() function to
srcu_check_read_flavor_force() and adds a read_flavor argument in order to
support an srcu_read_lock_fast() variant that is to avoid array indexing
in both the lock and unlock primitives.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Andrii Nakryiko <andrii@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: <bpf@...r.kernel.org>
---
 include/linux/srcu.h     |  2 +-
 include/linux/srcutiny.h |  2 +-
 include/linux/srcutree.h | 10 ++++++----
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index f6f779b9d9ff2..ca00b9af7c237 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -279,7 +279,7 @@ static inline int srcu_read_lock_lite(struct srcu_struct *ssp) __acquires(ssp)
 {
 	int retval;
 
-	srcu_check_read_flavor_lite(ssp);
+	srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_LITE);
 	retval = __srcu_read_lock_lite(ssp);
 	rcu_try_lock_acquire(&ssp->dep_map);
 	return retval;
diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h
index 31b59b4be2a74..6b1a7276aa4c9 100644
--- a/include/linux/srcutiny.h
+++ b/include/linux/srcutiny.h
@@ -82,7 +82,7 @@ static inline void srcu_barrier(struct srcu_struct *ssp)
 }
 
 #define srcu_check_read_flavor(ssp, read_flavor) do { } while (0)
-#define srcu_check_read_flavor_lite(ssp) do { } while (0)
+#define srcu_check_read_flavor_force(ssp, read_flavor) do { } while (0)
 
 /* Defined here to avoid size increase for non-torture kernels. */
 static inline void srcu_torture_stats_print(struct srcu_struct *ssp,
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 6b7eba59f3849..e29cc57eac81d 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -251,16 +251,18 @@ static inline void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx)
 
 void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor);
 
-// Record _lite() usage even for CONFIG_PROVE_RCU=n kernels.
-static inline void srcu_check_read_flavor_lite(struct srcu_struct *ssp)
+// Record reader usage even for CONFIG_PROVE_RCU=n kernels.  This is
+// needed only for flavors that require grace-period smp_mb() calls to be
+// promoted to synchronize_rcu().
+static inline void srcu_check_read_flavor_force(struct srcu_struct *ssp, int read_flavor)
 {
 	struct srcu_data *sdp = raw_cpu_ptr(ssp->sda);
 
-	if (likely(READ_ONCE(sdp->srcu_reader_flavor) & SRCU_READ_FLAVOR_LITE))
+	if (likely(READ_ONCE(sdp->srcu_reader_flavor) & read_flavor))
 		return;
 
 	// Note that the cmpxchg() in __srcu_check_read_flavor() is fully ordered.
-	__srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_LITE);
+	__srcu_check_read_flavor(ssp, read_flavor);
 }
 
 // Record non-_lite() usage only for CONFIG_PROVE_RCU=y kernels.
-- 
2.40.1