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Message-ID: <20231216032651.3553101-11-kent.overstreet@linux.dev>
Date: Fri, 15 Dec 2023 22:26:20 -0500
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: linux-kernel@...r.kernel.org,
linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org
Cc: Kent Overstreet <kent.overstreet@...ux.dev>,
tglx@...utronix.de,
x86@...nel.org,
tj@...nel.org,
peterz@...radead.org,
mathieu.desnoyers@...icios.com,
paulmck@...nel.org,
keescook@...omium.org,
dave.hansen@...ux.intel.com,
mingo@...hat.com,
will@...nel.org,
longman@...hat.com,
boqun.feng@...il.com,
brauner@...nel.org
Subject: [PATCH 21/50] locking/seqlock: Split out seqlock_types.h
Trimming down sched.h dependencies: we don't want to include more than
the base types.
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Will Deacon <will@...nel.org>
Cc: Waiman Long <longman@...hat.com>
Cc: Boqun Feng <boqun.feng@...il.com>
Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
---
include/linux/sched.h | 2 +-
include/linux/seqlock.h | 79 +----------------------------
include/linux/seqlock_types.h | 93 +++++++++++++++++++++++++++++++++++
3 files changed, 96 insertions(+), 78 deletions(-)
create mode 100644 include/linux/seqlock_types.h
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6d803d0904d9..436f7ce1450a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -33,7 +33,7 @@
#include <linux/task_io_accounting.h>
#include <linux/posix-timers_types.h>
#include <linux/rseq.h>
-#include <linux/seqlock.h>
+#include <linux/seqlock_types.h>
#include <linux/kcsan.h>
#include <linux/rv.h>
#include <linux/livepatch_sched.h>
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index e92f9d5577ba..d90d8ee29d81 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -18,6 +18,7 @@
#include <linux/lockdep.h>
#include <linux/mutex.h>
#include <linux/preempt.h>
+#include <linux/seqlock_types.h>
#include <linux/spinlock.h>
#include <asm/processor.h>
@@ -37,37 +38,6 @@
*/
#define KCSAN_SEQLOCK_REGION_MAX 1000
-/*
- * Sequence counters (seqcount_t)
- *
- * This is the raw counting mechanism, without any writer protection.
- *
- * Write side critical sections must be serialized and non-preemptible.
- *
- * If readers can be invoked from hardirq or softirq contexts,
- * interrupts or bottom halves must also be respectively disabled before
- * entering the write section.
- *
- * This mechanism can't be used if the protected data contains pointers,
- * as the writer can invalidate a pointer that a reader is following.
- *
- * If the write serialization mechanism is one of the common kernel
- * locking primitives, use a sequence counter with associated lock
- * (seqcount_LOCKNAME_t) instead.
- *
- * If it's desired to automatically handle the sequence counter writer
- * serialization and non-preemptibility requirements, use a sequential
- * lock (seqlock_t) instead.
- *
- * See Documentation/locking/seqlock.rst
- */
-typedef struct seqcount {
- unsigned sequence;
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
- struct lockdep_map dep_map;
-#endif
-} seqcount_t;
-
static inline void __seqcount_init(seqcount_t *s, const char *name,
struct lock_class_key *key)
{
@@ -131,28 +101,6 @@ static inline void seqcount_lockdep_reader_access(const seqcount_t *s)
* See Documentation/locking/seqlock.rst
*/
-/*
- * For PREEMPT_RT, seqcount_LOCKNAME_t write side critical sections cannot
- * disable preemption. It can lead to higher latencies, and the write side
- * sections will not be able to acquire locks which become sleeping locks
- * (e.g. spinlock_t).
- *
- * To remain preemptible while avoiding a possible livelock caused by the
- * reader preempting the writer, use a different technique: let the reader
- * detect if a seqcount_LOCKNAME_t writer is in progress. If that is the
- * case, acquire then release the associated LOCKNAME writer serialization
- * lock. This will allow any possibly-preempted writer to make progress
- * until the end of its writer serialization lock critical section.
- *
- * This lock-unlock technique must be implemented for all of PREEMPT_RT
- * sleeping locks. See Documentation/locking/locktypes.rst
- */
-#if defined(CONFIG_LOCKDEP) || defined(CONFIG_PREEMPT_RT)
-#define __SEQ_LOCK(expr) expr
-#else
-#define __SEQ_LOCK(expr)
-#endif
-
/*
* typedef seqcount_LOCKNAME_t - sequence counter with LOCKNAME associated
* @seqcount: The real sequence counter
@@ -194,11 +142,6 @@ static inline void seqcount_lockdep_reader_access(const seqcount_t *s)
* @lockbase: prefix for associated lock/unlock
*/
#define SEQCOUNT_LOCKNAME(lockname, locktype, preemptible, lockbase) \
-typedef struct seqcount_##lockname { \
- seqcount_t seqcount; \
- __SEQ_LOCK(locktype *lock); \
-} seqcount_##lockname##_t; \
- \
static __always_inline seqcount_t * \
__seqprop_##lockname##_ptr(seqcount_##lockname##_t *s) \
{ \
@@ -284,6 +227,7 @@ SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t, false, raw_spin)
SEQCOUNT_LOCKNAME(spinlock, spinlock_t, __SEQ_RT, spin)
SEQCOUNT_LOCKNAME(rwlock, rwlock_t, __SEQ_RT, read)
SEQCOUNT_LOCKNAME(mutex, struct mutex, true, mutex)
+#undef SEQCOUNT_LOCKNAME
/*
* SEQCNT_LOCKNAME_ZERO - static initializer for seqcount_LOCKNAME_t
@@ -794,25 +738,6 @@ static inline void raw_write_seqcount_latch(seqcount_latch_t *s)
smp_wmb(); /* increment "sequence" before following stores */
}
-/*
- * Sequential locks (seqlock_t)
- *
- * Sequence counters with an embedded spinlock for writer serialization
- * and non-preemptibility.
- *
- * For more info, see:
- * - Comments on top of seqcount_t
- * - Documentation/locking/seqlock.rst
- */
-typedef struct {
- /*
- * Make sure that readers don't starve writers on PREEMPT_RT: use
- * seqcount_spinlock_t instead of seqcount_t. Check __SEQ_LOCK().
- */
- seqcount_spinlock_t seqcount;
- spinlock_t lock;
-} seqlock_t;
-
#define __SEQLOCK_UNLOCKED(lockname) \
{ \
.seqcount = SEQCNT_SPINLOCK_ZERO(lockname, &(lockname).lock), \
diff --git a/include/linux/seqlock_types.h b/include/linux/seqlock_types.h
new file mode 100644
index 000000000000..dfdf43e3fa3d
--- /dev/null
+++ b/include/linux/seqlock_types.h
@@ -0,0 +1,93 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_SEQLOCK_TYPES_H
+#define __LINUX_SEQLOCK_TYPES_H
+
+#include <linux/lockdep_types.h>
+#include <linux/mutex_types.h>
+#include <linux/spinlock_types.h>
+
+/*
+ * Sequence counters (seqcount_t)
+ *
+ * This is the raw counting mechanism, without any writer protection.
+ *
+ * Write side critical sections must be serialized and non-preemptible.
+ *
+ * If readers can be invoked from hardirq or softirq contexts,
+ * interrupts or bottom halves must also be respectively disabled before
+ * entering the write section.
+ *
+ * This mechanism can't be used if the protected data contains pointers,
+ * as the writer can invalidate a pointer that a reader is following.
+ *
+ * If the write serialization mechanism is one of the common kernel
+ * locking primitives, use a sequence counter with associated lock
+ * (seqcount_LOCKNAME_t) instead.
+ *
+ * If it's desired to automatically handle the sequence counter writer
+ * serialization and non-preemptibility requirements, use a sequential
+ * lock (seqlock_t) instead.
+ *
+ * See Documentation/locking/seqlock.rst
+ */
+typedef struct seqcount {
+ unsigned sequence;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lockdep_map dep_map;
+#endif
+} seqcount_t;
+
+/*
+ * For PREEMPT_RT, seqcount_LOCKNAME_t write side critical sections cannot
+ * disable preemption. It can lead to higher latencies, and the write side
+ * sections will not be able to acquire locks which become sleeping locks
+ * (e.g. spinlock_t).
+ *
+ * To remain preemptible while avoiding a possible livelock caused by the
+ * reader preempting the writer, use a different technique: let the reader
+ * detect if a seqcount_LOCKNAME_t writer is in progress. If that is the
+ * case, acquire then release the associated LOCKNAME writer serialization
+ * lock. This will allow any possibly-preempted writer to make progress
+ * until the end of its writer serialization lock critical section.
+ *
+ * This lock-unlock technique must be implemented for all of PREEMPT_RT
+ * sleeping locks. See Documentation/locking/locktypes.rst
+ */
+#if defined(CONFIG_LOCKDEP) || defined(CONFIG_PREEMPT_RT)
+#define __SEQ_LOCK(expr) expr
+#else
+#define __SEQ_LOCK(expr)
+#endif
+
+#define SEQCOUNT_LOCKNAME(lockname, locktype, preemptible, lockbase) \
+typedef struct seqcount_##lockname { \
+ seqcount_t seqcount; \
+ __SEQ_LOCK(locktype *lock); \
+} seqcount_##lockname##_t;
+
+SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t, false, raw_spin)
+SEQCOUNT_LOCKNAME(spinlock, spinlock_t, __SEQ_RT, spin)
+SEQCOUNT_LOCKNAME(rwlock, rwlock_t, __SEQ_RT, read)
+SEQCOUNT_LOCKNAME(mutex, struct mutex, true, mutex)
+#undef SEQCOUNT_LOCKNAME
+
+/*
+ * Sequential locks (seqlock_t)
+ *
+ * Sequence counters with an embedded spinlock for writer serialization
+ * and non-preemptibility.
+ *
+ * For more info, see:
+ * - Comments on top of seqcount_t
+ * - Documentation/locking/seqlock.rst
+ */
+typedef struct {
+ /*
+ * Make sure that readers don't starve writers on PREEMPT_RT: use
+ * seqcount_spinlock_t instead of seqcount_t. Check __SEQ_LOCK().
+ */
+ seqcount_spinlock_t seqcount;
+ spinlock_t lock;
+} seqlock_t;
+
+#endif /* __LINUX_SEQLOCK_TYPES_H */
--
2.43.0
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