From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
rostedt@goodmis.org, "Paul E. McKenney" <paulmck@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
John Ogness <john.ogness@linutronix.de>,
Petr Mladek <pmladek@suse.com>
Subject: [PATCH RFC v2 rcu 1/8] srcu: Convert ->srcu_lock_count and ->srcu_unlock_count to atomic
Date: Thu, 29 Sep 2022 11:07:24 -0700 [thread overview]
Message-ID: <20220929180731.2875722-1-paulmck@kernel.org> (raw)
In-Reply-To: <20220929180714.GA2874192@paulmck-ThinkPad-P17-Gen-1>
NMI-safe variants of srcu_read_lock() and srcu_read_unlock() are needed
by printk(), which on many architectures entails read-modify-write
atomic operations. This commit prepares Tree SRCU for this change by
making both ->srcu_lock_count and ->srcu_unlock_count by atomic_long_t.
Link: https://lore.kernel.org/all/20220910221947.171557773@linutronix.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>
---
include/linux/srcutree.h | 4 ++--
kernel/rcu/srcutree.c | 24 ++++++++++++------------
2 files changed, 14 insertions(+), 14 deletions(-)
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index e3014319d1ad..0c4eca07d78d 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -23,8 +23,8 @@ struct srcu_struct;
*/
struct srcu_data {
/* Read-side state. */
- unsigned long srcu_lock_count[2]; /* Locks per CPU. */
- unsigned long srcu_unlock_count[2]; /* Unlocks per CPU. */
+ atomic_long_t srcu_lock_count[2]; /* Locks per CPU. */
+ atomic_long_t srcu_unlock_count[2]; /* Unlocks per CPU. */
/* Update-side state. */
spinlock_t __private lock ____cacheline_internodealigned_in_smp;
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 1c304fec89c0..6fd0665f4d1f 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -417,7 +417,7 @@ static unsigned long srcu_readers_lock_idx(struct srcu_struct *ssp, int idx)
for_each_possible_cpu(cpu) {
struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu);
- sum += READ_ONCE(cpuc->srcu_lock_count[idx]);
+ sum += atomic_long_read(&cpuc->srcu_lock_count[idx]);
}
return sum;
}
@@ -434,7 +434,7 @@ static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx)
for_each_possible_cpu(cpu) {
struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu);
- sum += READ_ONCE(cpuc->srcu_unlock_count[idx]);
+ sum += atomic_long_read(&cpuc->srcu_unlock_count[idx]);
}
return sum;
}
@@ -503,10 +503,10 @@ static bool srcu_readers_active(struct srcu_struct *ssp)
for_each_possible_cpu(cpu) {
struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu);
- sum += READ_ONCE(cpuc->srcu_lock_count[0]);
- sum += READ_ONCE(cpuc->srcu_lock_count[1]);
- sum -= READ_ONCE(cpuc->srcu_unlock_count[0]);
- sum -= READ_ONCE(cpuc->srcu_unlock_count[1]);
+ sum += atomic_long_read(&cpuc->srcu_lock_count[0]);
+ sum += atomic_long_read(&cpuc->srcu_lock_count[1]);
+ sum -= atomic_long_read(&cpuc->srcu_unlock_count[0]);
+ sum -= atomic_long_read(&cpuc->srcu_unlock_count[1]);
}
return sum;
}
@@ -636,7 +636,7 @@ int __srcu_read_lock(struct srcu_struct *ssp)
int idx;
idx = READ_ONCE(ssp->srcu_idx) & 0x1;
- this_cpu_inc(ssp->sda->srcu_lock_count[idx]);
+ this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter);
smp_mb(); /* B */ /* Avoid leaking the critical section. */
return idx;
}
@@ -650,7 +650,7 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
{
smp_mb(); /* C */ /* Avoid leaking the critical section. */
- this_cpu_inc(ssp->sda->srcu_unlock_count[idx]);
+ this_cpu_inc(ssp->sda->srcu_unlock_count[idx].counter);
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
@@ -1687,8 +1687,8 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf)
struct srcu_data *sdp;
sdp = per_cpu_ptr(ssp->sda, cpu);
- u0 = data_race(sdp->srcu_unlock_count[!idx]);
- u1 = data_race(sdp->srcu_unlock_count[idx]);
+ u0 = data_race(sdp->srcu_unlock_count[!idx].counter);
+ u1 = data_race(sdp->srcu_unlock_count[idx].counter);
/*
* Make sure that a lock is always counted if the corresponding
@@ -1696,8 +1696,8 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf)
*/
smp_rmb();
- l0 = data_race(sdp->srcu_lock_count[!idx]);
- l1 = data_race(sdp->srcu_lock_count[idx]);
+ l0 = data_race(sdp->srcu_lock_count[!idx].counter);
+ l1 = data_race(sdp->srcu_lock_count[idx].counter);
c0 = l0 - u0;
c1 = l1 - u1;
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2022-09-29 18:08 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 14:46 [PATCH rcu 0/4] NMI-safe SRCU reader API Paul E. McKenney
2022-09-21 14:46 ` [PATCH RFC rcu 1/4] srcu: Convert ->srcu_lock_count and ->srcu_unlock_count to atomic Paul E. McKenney
2022-09-21 14:46 ` [PATCH RFC rcu 2/4] srcu: Create and srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe() Paul E. McKenney
2022-09-21 14:46 ` [PATCH RFC rcu 3/4] srcu: Check for consistent per-CPU per-srcu_struct NMI safety Paul E. McKenney
2022-09-21 14:46 ` [PATCH RFC rcu 4/4] srcu: Check for consistent global " Paul E. McKenney
2022-09-29 18:07 ` [PATCH v2 rcu 0/8] NMI-safe SRCU reader API Paul E. McKenney
2022-09-29 18:07 ` Paul E. McKenney [this message]
2022-09-30 15:02 ` [PATCH RFC v2 rcu 1/8] srcu: Convert ->srcu_lock_count and ->srcu_unlock_count to atomic John Ogness
2022-09-30 15:35 ` Paul E. McKenney
2022-09-30 20:37 ` John Ogness
2022-10-01 16:51 ` Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 2/8] srcu: Create an srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe() Paul E. McKenney
2022-10-02 15:55 ` Frederic Weisbecker
2022-10-02 15:57 ` Frederic Weisbecker
2022-10-02 16:10 ` Paul E. McKenney
2022-10-02 16:09 ` Paul E. McKenney
2022-10-02 21:47 ` Frederic Weisbecker
2022-10-02 23:46 ` Paul E. McKenney
2022-10-03 9:55 ` Frederic Weisbecker
2022-10-03 11:52 ` Paul E. McKenney
2022-10-18 14:31 ` John Ogness
2022-10-18 15:18 ` Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 3/8] srcu: Check for consistent per-CPU per-srcu_struct NMI safety Paul E. McKenney
2022-10-02 22:06 ` Frederic Weisbecker
2022-10-02 23:51 ` Paul E. McKenney
2022-10-03 10:13 ` Frederic Weisbecker
2022-10-03 11:57 ` Paul E. McKenney
2022-10-03 12:37 ` Frederic Weisbecker
2022-10-03 13:32 ` Paul E. McKenney
2022-10-03 13:36 ` Frederic Weisbecker
2022-09-29 18:07 ` [PATCH RFC v2 rcu 4/8] srcu: Check for consistent global " Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 5/8] arch/x86: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 6/8] arch/arm64: " Paul E. McKenney
2022-10-05 11:12 ` Mark Rutland
2022-09-29 18:07 ` [PATCH RFC v2 rcu 7/8] arch/loongarch: " Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 8/8] arch/s390: " Paul E. McKenney
2022-10-03 14:11 ` [PATCH v2 rcu 0/8] NMI-safe SRCU reader API Frederic Weisbecker
2022-10-03 16:38 ` Paul E. McKenney
2022-10-14 22:47 ` Joel Fernandes
2022-10-14 22:52 ` Joel Fernandes
2022-10-18 10:33 ` John Ogness
2022-10-18 15:24 ` Paul E. McKenney
2022-10-18 18:44 ` John Ogness
2022-10-18 18:59 ` Paul E. McKenney
2022-10-18 21:57 ` Paul E. McKenney
2022-10-19 11:13 ` John Ogness
2022-10-19 19:14 ` Paul E. McKenney
2022-10-19 21:38 ` John Ogness
2022-10-19 22:05 ` Frederic Weisbecker
2022-10-20 22:27 ` Paul E. McKenney
2022-10-20 22:41 ` Paul E. McKenney
2022-10-21 12:27 ` John Ogness
2022-10-21 13:59 ` Paul E. McKenney
2022-10-21 18:41 ` Paul E. McKenney
2022-10-24 6:15 ` John Ogness
2022-10-24 13:47 ` Paul E. McKenney
2022-10-27 9:31 ` John Ogness
2022-10-27 14:10 ` Paul E. McKenney
2022-10-27 14:39 ` John Ogness
2022-10-27 16:01 ` Paul E. McKenney
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