locking: Introduce __cleanup() based infrastructure

Use __attribute__((__cleanup__(func))) to build:

 - simple auto-release pointers using __free()

 - 'classes' with constructor and destructor semantics for
   scope-based resource management.

 - lock guards based on the above classes.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230612093537.614161713%40infradead.org

diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
new file mode 100644 (file)
index 0000000..53f1a7a
--- /dev/null
+++ b/include/linux/cleanup.h
@@ -0,0 +1,171 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_GUARDS_H
+#define __LINUX_GUARDS_H
+
+#include <linux/compiler.h>
+
+/*
+ * DEFINE_FREE(name, type, free):
+ *     simple helper macro that defines the required wrapper for a __free()
+ *     based cleanup function. @free is an expression using '_T' to access
+ *     the variable.
+ *
+ * __free(name):
+ *     variable attribute to add a scoped based cleanup to the variable.
+ *
+ * no_free_ptr(var):
+ *     like a non-atomic xchg(var, NULL), such that the cleanup function will
+ *     be inhibited -- provided it sanely deals with a NULL value.
+ *
+ * return_ptr(p):
+ *     returns p while inhibiting the __free().
+ *
+ * Ex.
+ *
+ * DEFINE_FREE(kfree, void *, if (_T) kfree(_T))
+ *
+ *     struct obj *p __free(kfree) = kmalloc(...);
+ *     if (!p)
+ *             return NULL;
+ *
+ *     if (!init_obj(p))
+ *             return NULL;
+ *
+ *     return_ptr(p);
+ */
+
+#define DEFINE_FREE(_name, _type, _free) \
+       static inline void __free_##_name(void *p) { _type _T = *(_type *)p; _free; }
+
+#define __free(_name)  __cleanup(__free_##_name)
+
+#define no_free_ptr(p) \
+       ({ __auto_type __ptr = (p); (p) = NULL; __ptr; })
+
+#define return_ptr(p)  return no_free_ptr(p)
+
+
+/*
+ * DEFINE_CLASS(name, type, exit, init, init_args...):
+ *     helper to define the destructor and constructor for a type.
+ *     @exit is an expression using '_T' -- similar to FREE above.
+ *     @init is an expression in @init_args resulting in @type
+ *
+ * EXTEND_CLASS(name, ext, init, init_args...):
+ *     extends class @name to @name@ext with the new constructor
+ *
+ * CLASS(name, var)(args...):
+ *     declare the variable @var as an instance of the named class
+ *
+ * Ex.
+ *
+ * DEFINE_CLASS(fdget, struct fd, fdput(_T), fdget(fd), int fd)
+ *
+ *     CLASS(fdget, f)(fd);
+ *     if (!f.file)
+ *             return -EBADF;
+ *
+ *     // use 'f' without concern
+ */
+
+#define DEFINE_CLASS(_name, _type, _exit, _init, _init_args...)                \
+typedef _type class_##_name##_t;                                       \
+static inline void class_##_name##_destructor(_type *p)                        \
+{ _type _T = *p; _exit; }                                              \
+static inline _type class_##_name##_constructor(_init_args)            \
+{ _type t = _init; return t; }
+
+#define EXTEND_CLASS(_name, ext, _init, _init_args...)                 \
+typedef class_##_name##_t class_##_name##ext##_t;                      \
+static inline void class_##_name##ext##_destructor(class_##_name##_t *p)\
+{ class_##_name##_destructor(p); }                                     \
+static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
+{ class_##_name##_t t = _init; return t; }
+
+#define CLASS(_name, var)                                              \
+       class_##_name##_t var __cleanup(class_##_name##_destructor) =   \
+               class_##_name##_constructor
+
+
+/*
+ * DEFINE_GUARD(name, type, lock, unlock):
+ *     trivial wrapper around DEFINE_CLASS() above specifically
+ *     for locks.
+ *
+ * guard(name):
+ *     an anonymous instance of the (guard) class
+ *
+ * scoped_guard (name, args...) { }:
+ *     similar to CLASS(name, scope)(args), except the variable (with the
+ *     explicit name 'scope') is declard in a for-loop such that its scope is
+ *     bound to the next (compound) statement.
+ *
+ */
+
+#define DEFINE_GUARD(_name, _type, _lock, _unlock) \
+       DEFINE_CLASS(_name, _type, _unlock, ({ _lock; _T; }), _type _T)
+
+#define guard(_name) \
+       CLASS(_name, __UNIQUE_ID(guard))
+
+#define scoped_guard(_name, args...)                                   \
+       for (CLASS(_name, scope)(args),                                 \
+            *done = NULL; !done; done = (void *)1)
+
+/*
+ * Additional helper macros for generating lock guards with types, either for
+ * locks that don't have a native type (eg. RCU, preempt) or those that need a
+ * 'fat' pointer (eg. spin_lock_irqsave).
+ *
+ * DEFINE_LOCK_GUARD_0(name, lock, unlock, ...)
+ * DEFINE_LOCK_GUARD_1(name, type, lock, unlock, ...)
+ *
+ * will result in the following type:
+ *
+ *   typedef struct {
+ *     type *lock;             // 'type := void' for the _0 variant
+ *     __VA_ARGS__;
+ *   } class_##name##_t;
+ *
+ * As above, both _lock and _unlock are statements, except this time '_T' will
+ * be a pointer to the above struct.
+ */
+
+#define __DEFINE_UNLOCK_GUARD(_name, _type, _unlock, ...)              \
+typedef struct {                                                       \
+       _type *lock;                                                    \
+       __VA_ARGS__;                                                    \
+} class_##_name##_t;                                                   \
+                                                                       \
+static inline void class_##_name##_destructor(class_##_name##_t *_T)   \
+{                                                                      \
+       if (_T->lock) { _unlock; }                                      \
+}
+
+
+#define __DEFINE_LOCK_GUARD_1(_name, _type, _lock)                     \
+static inline class_##_name##_t class_##_name##_constructor(_type *l)  \
+{                                                                      \
+       class_##_name##_t _t = { .lock = l }, *_T = &_t;                \
+       _lock;                                                          \
+       return _t;                                                      \
+}
+
+#define __DEFINE_LOCK_GUARD_0(_name, _lock)                            \
+static inline class_##_name##_t class_##_name##_constructor(void)      \
+{                                                                      \
+       class_##_name##_t _t = { .lock = (void*)1 },                    \
+                        *_T __maybe_unused = &_t;                      \
+       _lock;                                                          \
+       return _t;                                                      \
+}
+
+#define DEFINE_LOCK_GUARD_1(_name, _type, _lock, _unlock, ...)         \
+__DEFINE_UNLOCK_GUARD(_name, _type, _unlock, __VA_ARGS__)              \
+__DEFINE_LOCK_GUARD_1(_name, _type, _lock)
+
+#define DEFINE_LOCK_GUARD_0(_name, _lock, _unlock, ...)                        \
+__DEFINE_UNLOCK_GUARD(_name, void, _unlock, __VA_ARGS__)               \
+__DEFINE_LOCK_GUARD_0(_name, _lock)
+
+#endif /* __LINUX_GUARDS_H */

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index 6cfd690..9b673fe 100644 (file)
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -5,6 +5,15 @@
 
 /* Compiler specific definitions for Clang compiler */
 
+/*
+ * Clang prior to 17 is being silly and considers many __cleanup() variables
+ * as unused (because they are, their sole purpose is to go out of scope).
+ *
+ * https://reviews.llvm.org/D152180
+ */
+#undef __cleanup
+#define __cleanup(func) __maybe_unused __attribute__((__cleanup__(func)))
+
 /* same as gcc, this was present in clang-2.6 so we can assume it works
  * with any version that can compile the kernel
  */

diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index e659cb6..081deae 100644 (file)
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -70,6 +70,12 @@
 #define __assume_aligned(a, ...)        __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
 
 /*
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-cleanup-variable-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#cleanup
+ */
+#define __cleanup(func)                        __attribute__((__cleanup__(func)))
+
+/*
  * Note the long name.
  *
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute

diff --git a/include/linux/device.h b/include/linux/device.h
index 472dd24..2b64268 100644 (file)
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -30,6 +30,7 @@
 #include <linux/device/bus.h>
 #include <linux/device/class.h>
 #include <linux/device/driver.h>
+#include <linux/cleanup.h>
 #include <asm/device.h>
 
 struct device;
@@ -899,6 +900,9 @@ void device_unregister(struct device *dev);
 void device_initialize(struct device *dev);
 int __must_check device_add(struct device *dev);
 void device_del(struct device *dev);
+
+DEFINE_FREE(device_del, struct device *, if (_T) device_del(_T))
+
 int device_for_each_child(struct device *dev, void *data,
                          int (*fn)(struct device *dev, void *data));
 int device_for_each_child_reverse(struct device *dev, void *data,
@@ -1066,6 +1070,9 @@ extern int (*platform_notify_remove)(struct device *dev);
  */
 struct device *get_device(struct device *dev);
 void put_device(struct device *dev);
+
+DEFINE_FREE(put_device, struct device *, if (_T) put_device(_T))
+
 bool kill_device(struct device *dev);
 
 #ifdef CONFIG_DEVTMPFS

diff --git a/include/linux/file.h b/include/linux/file.h
index 39704ea..6e9099d 100644 (file)
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -10,6 +10,7 @@
 #include <linux/types.h>
 #include <linux/posix_types.h>
 #include <linux/errno.h>
+#include <linux/cleanup.h>
 
 struct file;
 
@@ -80,6 +81,8 @@ static inline void fdput_pos(struct fd f)
        fdput(f);
 }
 
+DEFINE_CLASS(fd, struct fd, fdput(_T), fdget(fd), int fd)
+
 extern int f_dupfd(unsigned int from, struct file *file, unsigned flags);
 extern int replace_fd(unsigned fd, struct file *file, unsigned flags);
 extern void set_close_on_exec(unsigned int fd, int flag);
@@ -88,6 +91,9 @@ extern int __get_unused_fd_flags(unsigned flags, unsigned long nofile);
 extern int get_unused_fd_flags(unsigned flags);
 extern void put_unused_fd(unsigned int fd);
 
+DEFINE_CLASS(get_unused_fd, int, if (_T >= 0) put_unused_fd(_T),
+            get_unused_fd_flags(flags), unsigned flags)
+
 extern void fd_install(unsigned int fd, struct file *file);
 
 extern int __receive_fd(struct file *file, int __user *ufd,

diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index 5ec0fa7..2b665c3 100644 (file)
--- 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/cleanup.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_LOCK_GUARD_0(irq, local_irq_disable(), local_irq_enable())
+DEFINE_LOCK_GUARD_0(irqsave,
+                   local_irq_save(_T->flags),
+                   local_irq_restore(_T->flags),
+                   unsigned long flags)
+
 #endif

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 8f226d4..a33aa9e 100644 (file)
--- 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/cleanup.h>
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)                 \
@@ -219,4 +220,7 @@ extern void mutex_unlock(struct mutex *lock);
 
 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
 
+DEFINE_GUARD(mutex, struct mutex *, mutex_lock(_T), mutex_unlock(_T))
+DEFINE_FREE(mutex, struct mutex *, if (_T) mutex_unlock(_T))
+
 #endif /* __LINUX_MUTEX_H */

diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 1338ea2..d33ab17 100644 (file)
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -8,6 +8,7 @@
 #include <linux/cpumask.h>
 #include <linux/pfn.h>
 #include <linux/init.h>
+#include <linux/cleanup.h>
 
 #include <asm/percpu.h>
 
@@ -127,6 +128,9 @@ extern void __init setup_per_cpu_areas(void);
 extern void __percpu *__alloc_percpu_gfp(size_t size, size_t align, gfp_t gfp) __alloc_size(1);
 extern void __percpu *__alloc_percpu(size_t size, size_t align) __alloc_size(1);
 extern void free_percpu(void __percpu *__pdata);
+
+DEFINE_FREE(free_percpu, void __percpu *, free_percpu(_T))
+
 extern phys_addr_t per_cpu_ptr_to_phys(void *addr);
 
 #define alloc_percpu_gfp(type, gfp)                                    \

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 0df425b..1424670 100644 (file)
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -8,6 +8,7 @@
  */
 
 #include <linux/linkage.h>
+#include <linux/cleanup.h>
 #include <linux/list.h>
 
 /*
@@ -463,4 +464,8 @@ static __always_inline void preempt_enable_nested(void)
                preempt_enable();
 }
 
+DEFINE_LOCK_GUARD_0(preempt, preempt_disable(), preempt_enable())
+DEFINE_LOCK_GUARD_0(preempt_notrace, preempt_disable_notrace(), preempt_enable_notrace())
+DEFINE_LOCK_GUARD_0(migrate, migrate_disable(), migrate_enable())
+
 #endif /* __LINUX_PREEMPT_H */

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index dcd2cf1..7aa0903 100644 (file)
--- 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/cleanup.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 *rhp, rcu_callback_t f)
 extern int rcu_expedited;
 extern int rcu_normal;
 
+DEFINE_LOCK_GUARD_0(rcu, rcu_read_lock(), rcu_read_unlock())
+
 #endif /* __LINUX_RCUPDATE_H */

diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index efa5c32..1dd530c 100644 (file)
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -15,6 +15,7 @@
 #include <linux/spinlock.h>
 #include <linux/atomic.h>
 #include <linux/err.h>
+#include <linux/cleanup.h>
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 # define __RWSEM_DEP_MAP_INIT(lockname)                        \
@@ -201,6 +202,13 @@ extern void up_read(struct rw_semaphore *sem);
  */
 extern void up_write(struct rw_semaphore *sem);
 
+DEFINE_GUARD(rwsem_read, struct rw_semaphore *, down_read(_T), up_read(_T))
+DEFINE_GUARD(rwsem_write, struct rw_semaphore *, down_write(_T), up_write(_T))
+
+DEFINE_FREE(up_read, struct rw_semaphore *, if (_T) up_read(_T))
+DEFINE_FREE(up_write, struct rw_semaphore *, if (_T) up_write(_T))
+
+
 /*
  * downgrade write lock to read lock
  */

diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index e0f5ac9..dd35ce2 100644 (file)
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -125,6 +125,8 @@ static inline void put_task_struct(struct task_struct *t)
                __put_task_struct(t);
 }
 
+DEFINE_FREE(put_task, struct task_struct *, if (_T) put_task_struct(_T))
+
 static inline void put_task_struct_many(struct task_struct *t, int nr)
 {
        if (refcount_sub_and_test(nr, &t->usage))

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 6b3e155..c1fb57d 100644 (file)
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -17,6 +17,7 @@
 #include <linux/types.h>
 #include <linux/workqueue.h>
 #include <linux/percpu-refcount.h>
+#include <linux/cleanup.h>
 
 
 /*
@@ -211,6 +212,8 @@ void kfree(const void *objp);
 void kfree_sensitive(const void *objp);
 size_t __ksize(const void *objp);
 
+DEFINE_FREE(kfree, void *, if (_T) kfree(_T))
+
 /**
  * ksize - Report actual allocation size of associated object
  *

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index be48f1c..31d3d74 100644 (file)
--- 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/cleanup.h>
 #include <asm/barrier.h>
 #include <asm/mmiowb.h>
 
@@ -502,5 +503,35 @@ int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
 
 void free_bucket_spinlocks(spinlock_t *locks);
 
+DEFINE_LOCK_GUARD_1(raw_spinlock, raw_spinlock_t,
+                   raw_spin_lock(_T->lock),
+                   raw_spin_unlock(_T->lock))
+
+DEFINE_LOCK_GUARD_1(raw_spinlock_nested, raw_spinlock_t,
+                   raw_spin_lock_nested(_T->lock, SINGLE_DEPTH_NESTING),
+                   raw_spin_unlock(_T->lock))
+
+DEFINE_LOCK_GUARD_1(raw_spinlock_irq, raw_spinlock_t,
+                   raw_spin_lock_irq(_T->lock),
+                   raw_spin_unlock_irq(_T->lock))
+
+DEFINE_LOCK_GUARD_1(raw_spinlock_irqsave, raw_spinlock_t,
+                   raw_spin_lock_irqsave(_T->lock, _T->flags),
+                   raw_spin_unlock_irqrestore(_T->lock, _T->flags),
+                   unsigned long flags)
+
+DEFINE_LOCK_GUARD_1(spinlock, spinlock_t,
+                   spin_lock(_T->lock),
+                   spin_unlock(_T->lock))
+
+DEFINE_LOCK_GUARD_1(spinlock_irq, spinlock_t,
+                   spin_lock_irq(_T->lock),
+                   spin_unlock_irq(_T->lock))
+
+DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t,
+                   spin_lock_irqsave(_T->lock, _T->flags),
+                   spin_unlock_irqrestore(_T->lock, _T->flags),
+                   unsigned long flags)
+
 #undef __LINUX_INSIDE_SPINLOCK_H
 #endif /* __LINUX_SPINLOCK_H */

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 41c4b26..b3b1def 100644 (file)
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -343,4 +343,9 @@ static inline void smp_mb__after_srcu_read_unlock(void)
        /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
 }
 
+DEFINE_LOCK_GUARD_1(srcu, struct srcu_struct,
+                   _T->idx = srcu_read_lock(_T->lock),
+                   srcu_read_unlock(_T->lock, _T->idx),
+                   int idx)
+
 #endif

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index b30114d..3a6df9c 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5046,7 +5046,7 @@ sub process {
                                if|for|while|switch|return|case|
                                volatile|__volatile__|
                                __attribute__|format|__extension__|
-                               asm|__asm__)$/x)
+                               asm|__asm__|scoped_guard)$/x)
                        {
                        # cpp #define statements have non-optional spaces, ie
                        # if there is a space between the name and the open