include/qemu/lockable.h

   1 /*
   2  * Polymorphic locking functions (aka poor man templates)
   3  *
   4  * Copyright Red Hat, Inc. 2017, 2018
   5  *
   6  * Author: Paolo Bonzini <pbonzini@redhat.com>
   7  *
   8  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
   9  * See the COPYING.LIB file in the top-level directory.
  10  *
  11  */
  12
  13 #ifndef QEMU_LOCKABLE_H
  14 #define QEMU_LOCKABLE_H
  15
  16 #include "qemu/coroutine.h"
  17 #include "qemu/thread.h"
  18
  19 typedef void QemuLockUnlockFunc(void *);
  20
  21 struct QemuLockable {
  22     void *object;
  23     QemuLockUnlockFunc *lock;
  24     QemuLockUnlockFunc *unlock;
  25 };
  26
  27 /* This function gives an error if an invalid, non-NULL pointer type is passed
  28  * to QEMU_MAKE_LOCKABLE.  For optimized builds, we can rely on dead-code elimination
  29  * from the compiler, and give the errors already at link time.
  30  */
  31 #if defined(__OPTIMIZE__) && !defined(__SANITIZE_ADDRESS__)
  32 void unknown_lock_type(void *);
  33 #else
  34 static inline void unknown_lock_type(void *unused)
  35 {
  36     abort();
  37 }
  38 #endif
  39
  40 static inline __attribute__((__always_inline__)) QemuLockable *
  41 qemu_make_lockable(void *x, QemuLockable *lockable)
  42 {
  43     /* We cannot test this in a macro, otherwise we get compiler
  44      * warnings like "the address of 'm' will always evaluate as 'true'".
  45      */
  46     return x ? lockable : NULL;
  47 }
  48
  49 /* Auxiliary macros to simplify QEMU_MAKE_LOCABLE.  */
  50 #define QEMU_LOCK_FUNC(x) ((QemuLockUnlockFunc *)    \
  51     QEMU_GENERIC(x,                                  \
  52                  (QemuMutex *, qemu_mutex_lock),     \
  53                  (CoMutex *, qemu_co_mutex_lock),    \
  54                  (QemuSpin *, qemu_spin_lock),       \
  55                  unknown_lock_type))
  56
  57 #define QEMU_UNLOCK_FUNC(x) ((QemuLockUnlockFunc *)  \
  58     QEMU_GENERIC(x,                                  \
  59                  (QemuMutex *, qemu_mutex_unlock),   \
  60                  (CoMutex *, qemu_co_mutex_unlock),  \
  61                  (QemuSpin *, qemu_spin_unlock),     \
  62                  unknown_lock_type))
  63
  64 /* In C, compound literals have the lifetime of an automatic variable.
  65  * In C++ it would be different, but then C++ wouldn't need QemuLockable
  66  * either...
  67  */
  68 #define QEMU_MAKE_LOCKABLE_(x) qemu_make_lockable((x), &(QemuLockable) {    \
  69         .object = (x),                               \
  70         .lock = QEMU_LOCK_FUNC(x),                   \
  71         .unlock = QEMU_UNLOCK_FUNC(x),               \
  72     })
  73
  74 /* QEMU_MAKE_LOCKABLE - Make a polymorphic QemuLockable
  75  *
  76  * @x: a lock object (currently one of QemuMutex, CoMutex, QemuSpin).
  77  *
  78  * Returns a QemuLockable object that can be passed around
  79  * to a function that can operate with locks of any kind.
  80  */
  81 #define QEMU_MAKE_LOCKABLE(x)                        \
  82     QEMU_GENERIC(x,                                  \
  83                  (QemuLockable *, (x)),              \
  84                  QEMU_MAKE_LOCKABLE_(x))
  85
  86 static inline void qemu_lockable_lock(QemuLockable *x)
  87 {
  88     x->lock(x->object);
  89 }
  90
  91 static inline void qemu_lockable_unlock(QemuLockable *x)
  92 {
  93     x->unlock(x->object);
  94 }
  95
  96 #endif