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lockable: add QemuLockable

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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 <pbonzini@redhat.com>
Message-Id: <20180203153935.8056-3-pbonzini@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
This commit is contained in:
Paolo Bonzini
2018-02-03 10:39:32 -05:00
committed by Fam Zheng
parent 439b6e5efc
commit e70372fcaf
6 changed files with 168 additions and 5 deletions
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4
include/qemu/coroutine.h
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@ -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