[RFC][PATCH 1/2] locking: Introduce __cleanup__ based guards
From: Peter Zijlstra
Date: Fri May 26 2023 - 11:23:40 EST
Use __attribute__((__cleanup__(func))) to buid various guards:
- ptr_guard()
- void_guard() / void_scope()
- lock_guard() / lock_scope()
- double_lock_guard() / double_lock_scope()
Where the _guard thingies are variables with scope-based cleanup and
the _scope thingies are basically do-once for-loops with the same.
The CPP is rather impenetrable -- but I'll attempt to write proper
comments if/when people think this is worth pursuing.
Actual usage in the next patch
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
include/linux/compiler_attributes.h | 2
include/linux/irqflags.h | 7 ++
include/linux/guards.h | 118 ++++++++++++++++++++++++++++++++++++
include/linux/mutex.h | 5 +
include/linux/preempt.h | 4 +
include/linux/rcupdate.h | 3
include/linux/sched/task.h | 2
include/linux/spinlock.h | 23 +++++++
8 files changed, 164 insertions(+)
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -366,4 +366,6 @@
*/
#define __fix_address noinline __noclone
+#define __cleanup(func) __attribute__((__cleanup__(func)))
+
#endif /* __LINUX_COMPILER_ATTRIBUTES_H */
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -13,6 +13,7 @@
#define _LINUX_TRACE_IRQFLAGS_H
#include <linux/typecheck.h>
+#include <linux/guards.h>
#include <asm/irqflags.h>
#include <asm/percpu.h>
@@ -267,4 +268,10 @@ extern void warn_bogus_irq_restore(void)
#define irqs_disabled_flags(flags) raw_irqs_disabled_flags(flags)
+DEFINE_VOID_GUARD(irq, local_irq_disable(), local_irq_enable())
+DEFINE_VOID_GUARD(irqsave,
+ local_irq_save(_G->flags),
+ local_irq_restore(_G->flags),
+ unsigned long flags;)
+
#endif
--- /dev/null
+++ b/include/linux/guards.h
@@ -0,0 +1,118 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_GUARDS_H
+#define __LINUX_GUARDS_H
+
+#include <linux/compiler_attributes.h>
+
+/* Pointer Guard */
+
+#define DEFINE_PTR_GUARD(_type, _Type, _Put) \
+typedef _Type *ptr_guard_##_type##_t; \
+static inline void ptr_guard_##_type##_cleanup(_Type **_ptr) \
+{ \
+ _Type *_G = *_ptr; \
+ if (_G) \
+ _Put(_G); \
+}
+
+#define ptr_guard(_type, _name) \
+ ptr_guard_##_type##_t _name __cleanup(ptr_guard_##_type##_cleanup)
+
+
+/* Void Guard */
+
+#define DEFINE_VOID_GUARD(_type, _Lock, _Unlock, ...) \
+typedef struct { \
+ __VA_ARGS__ \
+} void_guard_##_type##_t; \
+ \
+static inline void void_guard_##_type##_cleanup(void *_g) \
+{ \
+ void_guard_##_type##_t *_G __maybe_unused = _g; \
+ _Unlock; \
+} \
+ \
+static inline void_guard_##_type##_t void_guard_##_type##_init(void) \
+{ \
+ void_guard_##_type##_t _g = { }, *_G __maybe_unused = &_g; \
+ _Lock; \
+ return _g; \
+}
+
+#define void_guard(_type, _name) \
+ void_guard_##_type##_t _name __cleanup(void_guard_##_type##_cleanup) = \
+ void_guard_##_type##_init()
+
+#define void_scope(_type) \
+ for (struct { void_guard_##_type##_t guard; bool done; } _scope \
+ __cleanup(void_guard_##_type##_cleanup) = \
+ { .guard = void_guard_##_type##_init() }; !_scope.done; \
+ _scope.done = true)
+
+
+/* Lock Guard */
+
+#define DEFINE_LOCK_GUARD(_type, _Type, _Lock, _Unlock, ...) \
+typedef struct { \
+ _Type *lock; \
+ __VA_ARGS__ \
+} lock_guard_##_type##_t; \
+ \
+static inline void lock_guard_##_type##_cleanup(void *_g) \
+{ \
+ lock_guard_##_type##_t *_G = _g; \
+ _Unlock; \
+} \
+ \
+static inline lock_guard_##_type##_t lock_guard_##_type##_init(_Type *lock) \
+{ \
+ lock_guard_##_type##_t _g = { .lock = lock }, *_G = &_g; \
+ _Lock; \
+ return _g; \
+}
+
+#define lock_guard(_type, _name, _ptr) \
+ lock_guard_##_type##_t _name __cleanup(lock_guard_##_type##_cleanup) = \
+ lock_guard_##_type##_init(_ptr)
+
+#define lock_scope(_type, _ptr) \
+ for (struct { lock_guard_##_type##_t guard; bool done; } _scope \
+ __cleanup(lock_guard_##_type##_cleanup) = \
+ { .guard = lock_guard_##_type##_init(_ptr) }; !_scope.done; \
+ _scope.done = true)
+
+
+/* Double Lock Guard */
+
+#define DEFINE_DOUBLE_LOCK_GUARD(_type, _Type, _Lock, _Unlock, ...) \
+typedef struct { \
+ _Type *lock; \
+ _Type *lock2; \
+ __VA_ARGS__ \
+} double_lock_guard_##_type##_t; \
+ \
+static inline void double_lock_guard_##_type##_cleanup(void *_g) \
+{ \
+ double_lock_guard_##_type##_t *_G = _g; \
+ _Unlock; \
+} \
+ \
+static inline double_lock_guard_##_type##_t double_lock_guard_##_type##_init(_Type *lock, _Type *lock2) \
+{ \
+ double_lock_guard_##_type##_t _g = { .lock = lock, .lock2 = lock2 }, *_G = &_g;\
+ _Lock; \
+ return _g; \
+}
+
+#define double_lock_guard(_type, _name, _ptr, _ptr2) \
+ double_lock_guard_##_type##_t _name __cleanup(double_lock_guard_##_type##_cleanup) = \
+ double_lock_guard_##_type##_init(_ptr, _ptr2)
+
+#define double_lock_scope(_type, _ptr, _ptr2) \
+ for (struct { double_lock_guard_##_type##_t guard; bool done; } _scope \
+ __cleanup(double_lock_guard_##_type##_cleanup) = \
+ { .guard = double_lock_guard_##_type##_init(_ptr, _ptr2) }; \
+ !_scope.done; _scope.done = true)
+
+
+#endif /* __LINUX_GUARDS_H */
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -19,6 +19,7 @@
#include <asm/processor.h>
#include <linux/osq_lock.h>
#include <linux/debug_locks.h>
+#include <linux/guards.h>
#ifdef CONFIG_DEBUG_LOCK_ALLOC
# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
@@ -219,4 +220,8 @@ extern void mutex_unlock(struct mutex *l
extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
+DEFINE_LOCK_GUARD(mutex, struct mutex,
+ mutex_lock(_G->lock),
+ mutex_unlock(_G->lock))
+
#endif /* __LINUX_MUTEX_H */
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -8,6 +8,7 @@
*/
#include <linux/linkage.h>
+#include <linux/guards.h>
#include <linux/list.h>
/*
@@ -463,4 +464,7 @@ static __always_inline void preempt_enab
preempt_enable();
}
+DEFINE_VOID_GUARD(preempt, preempt_disable(), preempt_enable())
+DEFINE_VOID_GUARD(migrate, migrate_disable(), migrate_enable())
+
#endif /* __LINUX_PREEMPT_H */
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -27,6 +27,7 @@
#include <linux/preempt.h>
#include <linux/bottom_half.h>
#include <linux/lockdep.h>
+#include <linux/guards.h>
#include <asm/processor.h>
#include <linux/cpumask.h>
#include <linux/context_tracking_irq.h>
@@ -1095,4 +1096,6 @@ rcu_head_after_call_rcu(struct rcu_head
extern int rcu_expedited;
extern int rcu_normal;
+DEFINE_VOID_GUARD(rcu, rcu_read_lock(), rcu_read_unlock())
+
#endif /* __LINUX_RCUPDATE_H */
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -126,6 +126,8 @@ static inline void put_task_struct(struc
__put_task_struct(t);
}
+DEFINE_PTR_GUARD(put_task, struct task_struct, put_task_struct)
+
static inline void put_task_struct_many(struct task_struct *t, int nr)
{
if (refcount_sub_and_test(nr, &t->usage))
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -61,6 +61,7 @@
#include <linux/stringify.h>
#include <linux/bottom_half.h>
#include <linux/lockdep.h>
+#include <linux/guards.h>
#include <asm/barrier.h>
#include <asm/mmiowb.h>
@@ -502,5 +503,27 @@ int __alloc_bucket_spinlocks(spinlock_t
void free_bucket_spinlocks(spinlock_t *locks);
+DEFINE_LOCK_GUARD(raw, raw_spinlock_t,
+ raw_spin_lock(_G->lock),
+ raw_spin_unlock(_G->lock))
+DEFINE_LOCK_GUARD(raw_irq, raw_spinlock_t,
+ raw_spin_lock_irq(_G->lock),
+ raw_spin_unlock_irq(_G->lock))
+DEFINE_LOCK_GUARD(raw_irqsave, raw_spinlock_t,
+ raw_spin_lock_irqsave(_G->lock, _G->flags),
+ raw_spin_unlock_irqrestore(_G->lock, _G->flags),
+ unsigned long flags;)
+
+DEFINE_LOCK_GUARD(spin, spinlock_t,
+ spin_lock(_G->lock),
+ spin_unlock(_G->lock))
+DEFINE_LOCK_GUARD(spin_irq, spinlock_t,
+ spin_lock_irq(_G->lock),
+ spin_unlock_irq(_G->lock))
+DEFINE_LOCK_GUARD(spin_irqsave, spinlock_t,
+ spin_lock_irqsave(_G->lock, _G->flags),
+ spin_unlock_irqrestore(_G->lock, _G->flags),
+ unsigned long flags;)
+
#undef __LINUX_INSIDE_SPINLOCK_H
#endif /* __LINUX_SPINLOCK_H */