| Message ID | 20221222114635.1251934-19-andrzej.hajda@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Introduce __xchg, non-atomic xchg | expand |
On Thu, Dec 22, 2022 at 12:46:34PM +0100, Andrzej Hajda wrote: > The pattern of setting variable with new value and returning old > one is very common in kernel. Usually atomicity of the operation > is not required, so xchg seems to be suboptimal and confusing in > such cases. FWIW, Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com> > --- > include/linux/non-atomic/xchg.h | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > create mode 100644 include/linux/non-atomic/xchg.h > > diff --git a/include/linux/non-atomic/xchg.h b/include/linux/non-atomic/xchg.h > new file mode 100644 > index 00000000000000..f7fa5dd746f37d > --- /dev/null > +++ b/include/linux/non-atomic/xchg.h > @@ -0,0 +1,19 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _LINUX_NON_ATOMIC_XCHG_H > +#define _LINUX_NON_ATOMIC_XCHG_H > + > +/** > + * __xchg - set variable pointed by @ptr to @val, return old value > + * @ptr: pointer to affected variable > + * @val: value to be written > + * > + * This is non-atomic variant of xchg. > + */ > +#define __xchg(ptr, val) ({ \ > + __auto_type __ptr = ptr; \ > + __auto_type __t = *__ptr; \ > + *__ptr = (val); \ > + __t; \ > +}) > + > +#endif > -- > 2.34.1 >
diff --git a/include/linux/non-atomic/xchg.h b/include/linux/non-atomic/xchg.h new file mode 100644 index 00000000000000..f7fa5dd746f37d --- /dev/null +++ b/include/linux/non-atomic/xchg.h @@ -0,0 +1,19 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_NON_ATOMIC_XCHG_H +#define _LINUX_NON_ATOMIC_XCHG_H + +/** + * __xchg - set variable pointed by @ptr to @val, return old value + * @ptr: pointer to affected variable + * @val: value to be written + * + * This is non-atomic variant of xchg. + */ +#define __xchg(ptr, val) ({ \ + __auto_type __ptr = ptr; \ + __auto_type __t = *__ptr; \ + *__ptr = (val); \ + __t; \ +}) + +#endif
The pattern of setting variable with new value and returning old one is very common in kernel. Usually atomicity of the operation is not required, so xchg seems to be suboptimal and confusing in such cases. Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com> --- include/linux/non-atomic/xchg.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) create mode 100644 include/linux/non-atomic/xchg.h