linux-kernel - [PATCH rcu 09/20] srcu: Add SRCU_READ_FLAVOR_SLOWGP to flag need for synchronize

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250224022214.12037-10-boqun.feng@gmail.com>
Date: Sun, 23 Feb 2025 18:22:03 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: rcu@...r.kernel.org
Cc: Lai Jiangshan <jiangshanlai@...il.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Uladzislau Rezki <urezki@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Shuah Khan <shuah@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	bpf@...r.kernel.org,
	Alexei Starovoitov <ast@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Kent Overstreet <kent.overstreet@...ux.dev>
Subject: [PATCH rcu 09/20] srcu: Add SRCU_READ_FLAVOR_SLOWGP to flag need for synchronize_rcu()

From: "Paul E. McKenney" <paulmck@...nel.org>

This commit switches from a direct test of SRCU_READ_FLAVOR_LITE to a new
SRCU_READ_FLAVOR_SLOWGP macro to check for substituting synchronize_rcu()
for smp_mb() in SRCU grace periods.  Right now, SRCU_READ_FLAVOR_SLOWGP
is exactly SRCU_READ_FLAVOR_LITE, but the addition of the _fast() flavor
of SRCU will change that.

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>
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
 include/linux/srcu.h  | 3 +++
 kernel/rcu/srcutree.c | 6 +++---
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index ca00b9af7c23..505f5bdce444 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -49,6 +49,9 @@ int init_srcu_struct(struct srcu_struct *ssp);
 #define SRCU_READ_FLAVOR_LITE	0x4		// srcu_read_lock_lite().
 #define SRCU_READ_FLAVOR_ALL   (SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_NMI | \
 				SRCU_READ_FLAVOR_LITE) // All of the above.
+#define SRCU_READ_FLAVOR_SLOWGP	SRCU_READ_FLAVOR_LITE
+						// Flavors requiring synchronize_rcu()
+						// instead of smp_mb().
 
 #ifdef CONFIG_TINY_SRCU
 #include <linux/srcutiny.h>
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 121dd290cae1..8b5c50bc98e5 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -449,7 +449,7 @@ static bool srcu_readers_lock_idx(struct srcu_struct *ssp, int idx, bool gp, uns
 	}
 	WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)),
 		  "Mixed reader flavors for srcu_struct at %ps.\n", ssp);
-	if (mask & SRCU_READ_FLAVOR_LITE && !gp)
+	if (mask & SRCU_READ_FLAVOR_SLOWGP && !gp)
 		return false;
 	return sum == unlocks;
 }
@@ -487,7 +487,7 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *ssp, int idx)
 	unsigned long unlocks;
 
 	unlocks = srcu_readers_unlock_idx(ssp, idx, &rdm);
-	did_gp = !!(rdm & SRCU_READ_FLAVOR_LITE);
+	did_gp = !!(rdm & SRCU_READ_FLAVOR_SLOWGP);
 
 	/*
 	 * Make sure that a lock is always counted if the corresponding
@@ -1205,7 +1205,7 @@ static bool srcu_should_expedite(struct srcu_struct *ssp)
 
 	check_init_srcu_struct(ssp);
 	/* If _lite() readers, don't do unsolicited expediting. */
-	if (this_cpu_read(ssp->sda->srcu_reader_flavor) & SRCU_READ_FLAVOR_LITE)
+	if (this_cpu_read(ssp->sda->srcu_reader_flavor) & SRCU_READ_FLAVOR_SLOWGP)
 		return false;
 	/* If the local srcu_data structure has callbacks, not idle.  */
 	sdp = raw_cpu_ptr(ssp->sda);
-- 
2.39.5 (Apple Git-154)