From e70372fcaffc99444edce400a5178cb196cddaf7 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Sat, 3 Feb 2018 10:39:32 -0500 Subject: lockable: add QemuLockable QemuLockable is a polymorphic lock type that takes an object and knows which function to use for locking and unlocking. The implementation could use C11 _Generic, but since the support is not very widespread I am instead using __builtin_choose_expr and __builtin_types_compatible_p, which are already used by include/qemu/atomic.h. QemuLockable can be used to implement lock guards, or to pass around a lock in such a way that a function can release it and re-acquire it. The next patch will do this for CoQueue. Signed-off-by: Paolo Bonzini Message-Id: <20180203153935.8056-3-pbonzini@redhat.com> Reviewed-by: Richard Henderson Reviewed-by: Stefan Hajnoczi Reviewed-by: Fam Zheng Signed-off-by: Fam Zheng --- include/qemu/compiler.h | 39 ++++++++++++++++++++ include/qemu/coroutine.h | 4 +- include/qemu/lockable.h | 96 ++++++++++++++++++++++++++++++++++++++++++++++++ include/qemu/thread.h | 5 +-- include/qemu/typedefs.h | 4 ++ tests/test-coroutine.c | 25 +++++++++++++ 6 files changed, 168 insertions(+), 5 deletions(-) create mode 100644 include/qemu/lockable.h diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h index 5fcc4f7ec7..2cbe6a4f16 100644 --- a/include/qemu/compiler.h +++ b/include/qemu/compiler.h @@ -114,5 +114,44 @@ #ifndef __has_feature #define __has_feature(x) 0 /* compatibility with non-clang compilers */ #endif +/* Implement C11 _Generic via GCC builtins. Example: + * + * QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x) + * + * The first argument is the discriminator. The last is the default value. + * The middle ones are tuples in "(type, expansion)" format. + */ + +/* First, find out the number of generic cases. */ +#define QEMU_GENERIC(x, ...) \ + QEMU_GENERIC_(typeof(x), __VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0) + +/* There will be extra arguments, but they are not used. */ +#define QEMU_GENERIC_(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, count, ...) \ + QEMU_GENERIC##count(x, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9) + +/* Two more helper macros, this time to extract items from a parenthesized + * list. + */ +#define QEMU_FIRST_(a, b) a +#define QEMU_SECOND_(a, b) b + +/* ... and a final one for the common part of the "recursion". */ +#define QEMU_GENERIC_IF(x, type_then, else_) \ + __builtin_choose_expr(__builtin_types_compatible_p(x, \ + QEMU_FIRST_ type_then), \ + QEMU_SECOND_ type_then, else_) + +/* CPP poor man's "recursion". */ +#define QEMU_GENERIC1(x, a0, ...) (a0) +#define QEMU_GENERIC2(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC1(x, __VA_ARGS__)) +#define QEMU_GENERIC3(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC2(x, __VA_ARGS__)) +#define QEMU_GENERIC4(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC3(x, __VA_ARGS__)) +#define QEMU_GENERIC5(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC4(x, __VA_ARGS__)) +#define QEMU_GENERIC6(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC5(x, __VA_ARGS__)) +#define QEMU_GENERIC7(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC6(x, __VA_ARGS__)) +#define QEMU_GENERIC8(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC7(x, __VA_ARGS__)) +#define QEMU_GENERIC9(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC8(x, __VA_ARGS__)) +#define QEMU_GENERIC10(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC9(x, __VA_ARGS__)) #endif /* COMPILER_H */ diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h index ce2eb73670..8a5129741c 100644 --- a/include/qemu/coroutine.h +++ b/include/qemu/coroutine.h @@ -121,7 +121,7 @@ bool qemu_coroutine_entered(Coroutine *co); * Provides a mutex that can be used to synchronise coroutines */ struct CoWaitRecord; -typedef struct CoMutex { +struct CoMutex { /* Count of pending lockers; 0 for a free mutex, 1 for an * uncontended mutex. */ @@ -142,7 +142,7 @@ typedef struct CoMutex { unsigned handoff, sequence; Coroutine *holder; -} CoMutex; +}; /** * Initialises a CoMutex. This must be called before any other operation is used diff --git a/include/qemu/lockable.h b/include/qemu/lockable.h new file mode 100644 index 0000000000..b6ed6c89ec --- /dev/null +++ b/include/qemu/lockable.h @@ -0,0 +1,96 @@ +/* + * Polymorphic locking functions (aka poor man templates) + * + * Copyright Red Hat, Inc. 2017, 2018 + * + * Author: Paolo Bonzini + * + * This work is licensed under the terms of the GNU LGPL, version 2 or later. + * See the COPYING.LIB file in the top-level directory. + * + */ + +#ifndef QEMU_LOCKABLE_H +#define QEMU_LOCKABLE_H + +#include "qemu/coroutine.h" +#include "qemu/thread.h" + +typedef void QemuLockUnlockFunc(void *); + +struct QemuLockable { + void *object; + QemuLockUnlockFunc *lock; + QemuLockUnlockFunc *unlock; +}; + +/* This function gives an error if an invalid, non-NULL pointer type is passed + * to QEMU_MAKE_LOCKABLE. For optimized builds, we can rely on dead-code elimination + * from the compiler, and give the errors already at link time. + */ +#ifdef __OPTIMIZE__ +void unknown_lock_type(void *); +#else +static inline void unknown_lock_type(void *unused) +{ + abort(); +} +#endif + +static inline __attribute__((__always_inline__)) QemuLockable * +qemu_make_lockable(void *x, QemuLockable *lockable) +{ + /* We cannot test this in a macro, otherwise we get compiler + * warnings like "the address of 'm' will always evaluate as 'true'". + */ + return x ? lockable : NULL; +} + +/* Auxiliary macros to simplify QEMU_MAKE_LOCABLE. */ +#define QEMU_LOCK_FUNC(x) ((QemuLockUnlockFunc *) \ + QEMU_GENERIC(x, \ + (QemuMutex *, qemu_mutex_lock), \ + (CoMutex *, qemu_co_mutex_lock), \ + (QemuSpin *, qemu_spin_lock), \ + unknown_lock_type)) + +#define QEMU_UNLOCK_FUNC(x) ((QemuLockUnlockFunc *) \ + QEMU_GENERIC(x, \ + (QemuMutex *, qemu_mutex_unlock), \ + (CoMutex *, qemu_co_mutex_unlock), \ + (QemuSpin *, qemu_spin_unlock), \ + unknown_lock_type)) + +/* In C, compound literals have the lifetime of an automatic variable. + * In C++ it would be different, but then C++ wouldn't need QemuLockable + * either... + */ +#define QEMU_MAKE_LOCKABLE_(x) qemu_make_lockable((x), &(QemuLockable) { \ + .object = (x), \ + .lock = QEMU_LOCK_FUNC(x), \ + .unlock = QEMU_UNLOCK_FUNC(x), \ + }) + +/* QEMU_MAKE_LOCKABLE - Make a polymorphic QemuLockable + * + * @x: a lock object (currently one of QemuMutex, CoMutex, QemuSpin). + * + * Returns a QemuLockable object that can be passed around + * to a function that can operate with locks of any kind. + */ +#define QEMU_MAKE_LOCKABLE(x) \ + QEMU_GENERIC(x, \ + (QemuLockable *, (x)), \ + QEMU_MAKE_LOCKABLE_(x)) + +static inline void qemu_lockable_lock(QemuLockable *x) +{ + x->lock(x->object); +} + +static inline void qemu_lockable_unlock(QemuLockable *x) +{ + x->unlock(x->object); +} + +#endif diff --git a/include/qemu/thread.h b/include/qemu/thread.h index 9af4e945aa..ef7bd16123 100644 --- a/include/qemu/thread.h +++ b/include/qemu/thread.h @@ -4,7 +4,6 @@ #include "qemu/processor.h" #include "qemu/atomic.h" -typedef struct QemuMutex QemuMutex; typedef struct QemuCond QemuCond; typedef struct QemuSemaphore QemuSemaphore; typedef struct QemuEvent QemuEvent; @@ -97,9 +96,9 @@ struct Notifier; void qemu_thread_atexit_add(struct Notifier *notifier); void qemu_thread_atexit_remove(struct Notifier *notifier); -typedef struct QemuSpin { +struct QemuSpin { int value; -} QemuSpin; +}; static inline void qemu_spin_init(QemuSpin *spin) { diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h index 9bd7a834ba..5923849cdd 100644 --- a/include/qemu/typedefs.h +++ b/include/qemu/typedefs.h @@ -19,6 +19,7 @@ typedef struct BusClass BusClass; typedef struct BusState BusState; typedef struct Chardev Chardev; typedef struct CompatProperty CompatProperty; +typedef struct CoMutex CoMutex; typedef struct CPUAddressSpace CPUAddressSpace; typedef struct CPUState CPUState; typedef struct DeviceListener DeviceListener; @@ -86,9 +87,12 @@ typedef struct QEMUBH QEMUBH; typedef struct QemuConsole QemuConsole; typedef struct QemuDmaBuf QemuDmaBuf; typedef struct QEMUFile QEMUFile; +typedef struct QemuLockable QemuLockable; +typedef struct QemuMutex QemuMutex; typedef struct QemuOpt QemuOpt; typedef struct QemuOpts QemuOpts; typedef struct QemuOptsList QemuOptsList; +typedef struct QemuSpin QemuSpin; typedef struct QEMUSGList QEMUSGList; typedef struct QEMUTimer QEMUTimer; typedef struct QEMUTimerListGroup QEMUTimerListGroup; diff --git a/tests/test-coroutine.c b/tests/test-coroutine.c index ab8fdf701e..28e79b3210 100644 --- a/tests/test-coroutine.c +++ b/tests/test-coroutine.c @@ -14,6 +14,7 @@ #include "qemu/osdep.h" #include "qemu/coroutine.h" #include "qemu/coroutine_int.h" +#include "qemu/lockable.h" /* * Check that qemu_in_coroutine() works @@ -210,6 +211,18 @@ static void coroutine_fn mutex_fn(void *opaque) done++; } +static void coroutine_fn lockable_fn(void *opaque) +{ + QemuLockable *x = opaque; + qemu_lockable_lock(x); + assert(!locked); + locked = true; + qemu_coroutine_yield(); + locked = false; + qemu_lockable_unlock(x); + done++; +} + static void do_test_co_mutex(CoroutineEntry *entry, void *opaque) { Coroutine *c1 = qemu_coroutine_create(entry, opaque); @@ -240,6 +253,17 @@ static void test_co_mutex(void) do_test_co_mutex(mutex_fn, &m); } +static void test_co_mutex_lockable(void) +{ + CoMutex m; + CoMutex *null_pointer = NULL; + + qemu_co_mutex_init(&m); + do_test_co_mutex(lockable_fn, QEMU_MAKE_LOCKABLE(&m)); + + g_assert(QEMU_MAKE_LOCKABLE(null_pointer) == NULL); +} + /* * Check that creation, enter, and return work */ @@ -478,6 +502,7 @@ int main(int argc, char **argv) g_test_add_func("/basic/in_coroutine", test_in_coroutine); g_test_add_func("/basic/order", test_order); g_test_add_func("/locking/co-mutex", test_co_mutex); + g_test_add_func("/locking/co-mutex/lockable", test_co_mutex_lockable); if (g_test_perf()) { g_test_add_func("/perf/lifecycle", perf_lifecycle); g_test_add_func("/perf/nesting", perf_nesting); -- cgit v1.2.3