On 25 Sep 2021 at 03:43, Eric Sandeen wrote: > On 9/24/21 9:09 AM, Chandan Babu R wrote: >> From: Dave Chinner <dchinner@xxxxxxxxxx> >> Now we have liburcu, we can make use of it's atomic variable >> implementation. It is almost identical to the kernel API - it's just >> got a "uatomic" prefix. liburcu also provides all the same aomtic >> variable memory barriers as the kernel, so if we pull memory barrier >> dependent kernel code across, it will just work with the right >> barrier wrappers. >> This is preparation the addition of more extensive atomic operations >> the that kernel buffer cache requires to function correctly. >> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> >> [chandan.babu@xxxxxxxxxx: Swap order of arguments provided to atomic[64]_[add|sub]()] >> Signed-off-by: Chandan Babu R <chandan.babu@xxxxxxxxxx> >> --- >> include/atomic.h | 65 ++++++++++++++++++++++++++++++++++++++++-------- >> 1 file changed, 54 insertions(+), 11 deletions(-) >> diff --git a/include/atomic.h b/include/atomic.h >> index e0e1ba84..99cb85d3 100644 >> --- a/include/atomic.h >> +++ b/include/atomic.h >> @@ -7,21 +7,64 @@ >> #define __ATOMIC_H__ >> /* >> - * Warning: These are not really atomic at all. They are wrappers around the >> - * kernel atomic variable interface. If we do need these variables to be atomic >> - * (due to multithreading of the code that uses them) we need to add some >> - * pthreads magic here. >> + * Atomics are provided by liburcu. >> + * >> + * API and guidelines for which operations provide memory barriers is here: >> + * >> + * https://github.com/urcu/userspace-rcu/blob/master/doc/uatomic-api.md >> + * >> + * Unlike the kernel, the same interface supports 32 and 64 bit atomic integers. > > Given this, anyone have any objection to putting the #defines together at the > top, rather than hiding the 64 variants at the end of the file? > I don't see any issue in doing that. >> */ >> +#include <urcu/uatomic.h> >> +#include "spinlock.h" >> + >> typedef int32_t atomic_t; >> typedef int64_t atomic64_t; >> -#define atomic_inc_return(x) (++(*(x))) >> -#define atomic_dec_return(x) (--(*(x))) >> +#define atomic_read(a) uatomic_read(a) >> +#define atomic_set(a, v) uatomic_set(a, v) >> +#define atomic_add(v, a) uatomic_add(a, v) >> +#define atomic_sub(v, a) uatomic_sub(a, v) >> +#define atomic_inc(a) uatomic_inc(a) >> +#define atomic_dec(a) uatomic_dec(a) >> +#define atomic_inc_return(a) uatomic_add_return(a, 1) >> +#define atomic_dec_return(a) uatomic_sub_return(a, 1) >> +#define atomic_dec_and_test(a) (atomic_dec_return(a) == 0) >> +#define cmpxchg(a, o, n) uatomic_cmpxchg(a, o, n); > > and I'll fix this whitespace. > > Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx> Thanks for the reviews. -- chandan
