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Message-Id: <20251105203216.2701005-12-paulmck@kernel.org>
Date: Wed, 5 Nov 2025 12:32:12 -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>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
bpf@...r.kernel.org
Subject: [PATCH v2 12/16] srcu: Add SRCU_READ_FLAVOR_FAST_UPDOWN CPP macro
This commit adds the SRCU_READ_FLAVOR_FAST_UPDOWN=0x8 macro
and adjusts rcutorture to make use of it. In this commit, both
SRCU_READ_FLAVOR_FAST=0x4 and the new SRCU_READ_FLAVOR_FAST_UPDOWN
test SRCU-fast. When the SRCU-fast-updown is added, the new
SRCU_READ_FLAVOR_FAST_UPDOWN macro will test it when passed to the
rcutorture.reader_flavor module parameter.
The old SRCU_READ_FLAVOR_FAST macro's value changed from 0x8 to 0x4.
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: <bpf@...r.kernel.org>
---
include/linux/srcu.h | 16 +++++++++-------
kernel/rcu/rcutorture.c | 24 ++++++++++++++++++------
2 files changed, 27 insertions(+), 13 deletions(-)
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 41e27c1d917d..1dd6812aabe7 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -56,13 +56,15 @@ int init_srcu_struct_fast(struct srcu_struct *ssp);
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
/* Values for SRCU Tree srcu_data ->srcu_reader_flavor, but also used by rcutorture. */
-#define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock().
-#define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe().
-// 0x4 // SRCU-lite is no longer with us.
-#define SRCU_READ_FLAVOR_FAST 0x8 // srcu_read_lock_fast().
-#define SRCU_READ_FLAVOR_ALL (SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_NMI | \
- SRCU_READ_FLAVOR_FAST) // All of the above.
-#define SRCU_READ_FLAVOR_SLOWGP SRCU_READ_FLAVOR_FAST
+#define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock().
+#define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe().
+// 0x4 // SRCU-lite is no longer with us.
+#define SRCU_READ_FLAVOR_FAST 0x4 // srcu_read_lock_fast().
+#define SRCU_READ_FLAVOR_FAST_UPDOWN 0x8 // srcu_read_lock_fast().
+#define SRCU_READ_FLAVOR_ALL (SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_NMI | \
+ SRCU_READ_FLAVOR_FAST | SRCU_READ_FLAVOR_FAST_UPDOWN)
+ // All of the above.
+#define SRCU_READ_FLAVOR_SLOWGP (SRCU_READ_FLAVOR_FAST | SRCU_READ_FLAVOR_FAST_UPDOWN)
// Flavors requiring synchronize_rcu()
// instead of smp_mb().
void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 8022d32be351..70ee838cab55 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -702,6 +702,8 @@ static void srcu_torture_init(void)
rcu_sync_torture_init();
if (reader_flavor & SRCU_READ_FLAVOR_FAST)
srcu_ctlp = &srcu_ctlf;
+ if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN)
+ srcu_ctlp = &srcu_ctlf;
}
static void srcu_get_gp_data(int *flags, unsigned long *gp_seq)
@@ -728,6 +730,12 @@ static int srcu_torture_read_lock(void)
ret += idx << 1;
}
if (reader_flavor & SRCU_READ_FLAVOR_FAST) {
+ scp = srcu_read_lock_fast(srcu_ctlp);
+ idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
+ WARN_ON_ONCE(idx & ~0x1);
+ ret += idx << 2;
+ }
+ if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN) {
scp = srcu_read_lock_fast(srcu_ctlp);
idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
WARN_ON_ONCE(idx & ~0x1);
@@ -758,8 +766,10 @@ srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
static void srcu_torture_read_unlock(int idx)
{
WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1)));
- if (reader_flavor & SRCU_READ_FLAVOR_FAST)
+ if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN)
srcu_read_unlock_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 3));
+ if (reader_flavor & SRCU_READ_FLAVOR_FAST)
+ srcu_read_unlock_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 2));
if (reader_flavor & SRCU_READ_FLAVOR_NMI)
srcu_read_unlock_nmisafe(srcu_ctlp, (idx & 0x2) >> 1);
if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) || !(reader_flavor & SRCU_READ_FLAVOR_ALL))
@@ -793,7 +803,7 @@ static int srcu_torture_down_read(void)
WARN_ON_ONCE(idx & ~0x1);
return idx;
}
- if (reader_flavor & SRCU_READ_FLAVOR_FAST) {
+ if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN) {
scp = srcu_down_read_fast(srcu_ctlp);
idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
WARN_ON_ONCE(idx & ~0x1);
@@ -806,7 +816,7 @@ static int srcu_torture_down_read(void)
static void srcu_torture_up_read(int idx)
{
WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1)));
- if (reader_flavor & SRCU_READ_FLAVOR_FAST)
+ if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN)
srcu_up_read_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 3));
else if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) ||
!(reader_flavor & SRCU_READ_FLAVOR_ALL))
@@ -901,14 +911,16 @@ static struct rcu_torture_ops srcu_ops = {
.no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU),
.debug_objects = 1,
.have_up_down = IS_ENABLED(CONFIG_TINY_SRCU)
- ? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST,
+ ? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST_UPDOWN,
.name = "srcu"
};
static void srcud_torture_init(void)
{
rcu_sync_torture_init();
- if (reader_flavor & SRCU_READ_FLAVOR_FAST)
+ if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN)
+ WARN_ON(init_srcu_struct_fast(&srcu_ctld));
+ else if (reader_flavor & SRCU_READ_FLAVOR_FAST)
WARN_ON(init_srcu_struct_fast(&srcu_ctld));
else
WARN_ON(init_srcu_struct(&srcu_ctld));
@@ -953,7 +965,7 @@ static struct rcu_torture_ops srcud_ops = {
.no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU),
.debug_objects = 1,
.have_up_down = IS_ENABLED(CONFIG_TINY_SRCU)
- ? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST,
+ ? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST_UPDOWN,
.name = "srcud"
};
--
2.40.1
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