| Message ID | 1460050358-25025-7-git-send-email-cota@braap.org |
|---|---|
| State | New |
| Headers | show |
Emilio G. Cota <cota@braap.org> writes: > From: Guillaume Delbergue <guillaume.delbergue@greensocs.com> > > Signed-off-by: Guillaume Delbergue <guillaume.delbergue@greensocs.com> > [Rewritten. - Paolo] > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > include/qemu/thread.h | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) > > diff --git a/include/qemu/thread.h b/include/qemu/thread.h > index bdae6df..1aa843b 100644 > --- a/include/qemu/thread.h > +++ b/include/qemu/thread.h > @@ -1,6 +1,8 @@ > #ifndef __QEMU_THREAD_H > #define __QEMU_THREAD_H 1 > > +#include <errno.h> > +#include "qemu/atomic.h" > > typedef struct QemuMutex QemuMutex; > typedef struct QemuCond QemuCond; > @@ -60,4 +62,33 @@ struct Notifier; > void qemu_thread_atexit_add(struct Notifier *notifier); > void qemu_thread_atexit_remove(struct Notifier *notifier); > > +typedef struct QemuSpin { > + int value; If we are throwing true and false around as the only two values can we use bool here and be consistent when setting/clearing. > +} QemuSpin; > + > +static inline void qemu_spin_init(QemuSpin *spin) > +{ > + spin->value = 0; > +} > + > +static inline void qemu_spin_lock(QemuSpin *spin) > +{ > + do { > + while (atomic_read(&spin->value)); > + } while (atomic_xchg(&spin->value, true)); > +} > + > +static inline int qemu_spin_trylock(QemuSpin *spin) > +{ > + if (atomic_read(&spin->value) || atomic_xchg(&spin->value, true)) { > + return -EBUSY; > + } > + return 0; > +} > + > +static inline void qemu_spin_unlock(QemuSpin *spin) > +{ > + atomic_mb_set(&spin->value, 0); > +} > + > #endif -- Alex Bennée
On 04/07/2016 10:32 AM, Emilio G. Cota wrote:
> + while (atomic_read(&spin->value));
I really really don't like ; snuggled up behind loop conditions.
Isn't this where you want to use pause, anyway?
r~
On 04/08/2016 06:02 AM, Alex Bennée wrote: >> > +typedef struct QemuSpin { >> > + int value; > If we are throwing true and false around as the only two values can we > use bool here and be consistent when setting/clearing. > Except that quite a lot of hosts can only (efficiently) do atomic operations on a minimum of 4 byte quantities. I'd rather continue to use int here. r~
Richard Henderson <rth@twiddle.net> writes: > On 04/08/2016 06:02 AM, Alex Bennée wrote: >>> > +typedef struct QemuSpin { >>> > + int value; >> If we are throwing true and false around as the only two values can we >> use bool here and be consistent when setting/clearing. >> > > Except that quite a lot of hosts can only (efficiently) do atomic operations on > a minimum of 4 byte quantities. I'd rather continue to use int here. I suspect bool == unsigned int underneath. But having true/false and 0/1 mixed up gets confusing even if they are equivalent. > > > r~ -- Alex Bennée
On 08/04/2016 23:24, Alex Bennée wrote: > > Except that quite a lot of hosts can only (efficiently) do atomic operations on > > a minimum of 4 byte quantities. I'd rather continue to use int here. > > I suspect bool == unsigned int underneath. But having true/false and 0/1 mixed up > gets confusing even if they are equivalent. Sometimes sizeof(bool) == 1. Paolo
On 04/08/2016 02:26 PM, Paolo Bonzini wrote: > > > On 08/04/2016 23:24, Alex Bennée wrote: >>> Except that quite a lot of hosts can only (efficiently) do atomic operations on >>> a minimum of 4 byte quantities. I'd rather continue to use int here. >> >> I suspect bool == unsigned int underneath. But having true/false and 0/1 mixed up >> gets confusing even if they are equivalent. > > Sometimes sizeof(bool) == 1. sizeof(bool) == 1 everywhere except MacOSX, where it's 4. r~
On 09/04/16 00:31, Richard Henderson wrote: > On 04/08/2016 02:26 PM, Paolo Bonzini wrote: >> >> On 08/04/2016 23:24, Alex Bennée wrote: >>>> Except that quite a lot of hosts can only (efficiently) do atomic operations on >>>> a minimum of 4 byte quantities. I'd rather continue to use int here. >>> I suspect bool == unsigned int underneath. But having true/false and 0/1 mixed up >>> gets confusing even if they are equivalent. >> Sometimes sizeof(bool) == 1. > sizeof(bool) == 1 everywhere except MacOSX, where it's 4. > Hm, that's too strange: $ gcc a.c a.c: In function ‘main’: a.c:6:5: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘long unsigned int’ [-Wformat=] printf("%d\n", sizeof(bool)); ^ $ ./a.out 1 Kind regards, Sergey
diff --git a/include/qemu/thread.h b/include/qemu/thread.h index bdae6df..1aa843b 100644 --- a/include/qemu/thread.h +++ b/include/qemu/thread.h @@ -1,6 +1,8 @@ #ifndef __QEMU_THREAD_H #define __QEMU_THREAD_H 1 +#include <errno.h> +#include "qemu/atomic.h" typedef struct QemuMutex QemuMutex; typedef struct QemuCond QemuCond; @@ -60,4 +62,33 @@ struct Notifier; void qemu_thread_atexit_add(struct Notifier *notifier); void qemu_thread_atexit_remove(struct Notifier *notifier); +typedef struct QemuSpin { + int value; +} QemuSpin; + +static inline void qemu_spin_init(QemuSpin *spin) +{ + spin->value = 0; +} + +static inline void qemu_spin_lock(QemuSpin *spin) +{ + do { + while (atomic_read(&spin->value)); + } while (atomic_xchg(&spin->value, true)); +} + +static inline int qemu_spin_trylock(QemuSpin *spin) +{ + if (atomic_read(&spin->value) || atomic_xchg(&spin->value, true)) { + return -EBUSY; + } + return 0; +} + +static inline void qemu_spin_unlock(QemuSpin *spin) +{ + atomic_mb_set(&spin->value, 0); +} + #endif