On (01/18/16 15:36), Minchan Kim wrote: [..] > > --- a/mm/zsmalloc.c > > +++ b/mm/zsmalloc.c > > @@ -1635,8 +1635,8 @@ static int migrate_zspage(struct zs_pool *pool, struct size_class *class, > > free_obj = obj_malloc(d_page, class, handle); > > zs_object_copy(free_obj, used_obj, class); > > index++; > > + /* This also effectively unpins the handle */ > > As reply of Vlastimil, I relied that I guess it doesn't work. > We shouldn't omit unpin_tag and we should add WRITE_ONCE in > record_obj. > > As well, it's worth to dobule check with locking guys. > I will send updated version. but would WRITE_ONCE() tell the compiler that there is a dependency? __write_once_size() does not even issue a barrier for sizes <= 8 (our case). include/linux/compiler.h static __always_inline void __write_once_size(volatile void *p, void *res, int size) { switch (size) { case 1: *(volatile __u8 *)p = *(__u8 *)res; break; case 2: *(volatile __u16 *)p = *(__u16 *)res; break; case 4: *(volatile __u32 *)p = *(__u32 *)res; break; case 8: *(volatile __u64 *)p = *(__u64 *)res; break; default: barrier(); __builtin_memcpy((void *)p, (const void *)res, size); barrier(); } } #define WRITE_ONCE(x, val) \ ({ \ union { typeof(x) __val; char __c[1]; } __u = \ { .__val = (__force typeof(x)) (val) }; \ __write_once_size(&(x), __u.__c, sizeof(x)); \ __u.__val; \ }) so, even if clear_bit_unlock/test_and_set_bit_lock do smp_mb or barrier(), there is no corresponding barrier from record_obj()->WRITE_ONCE(). so I don't think WRITE_ONCE() will help the compiler, or am I missing something? .... add a barrier() to record_obj()? -ss -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>