On 2022/6/21 11:39, Muchun Song wrote: > On Tue, Jun 21, 2022 at 09:14:00AM +0800, Huang, Ying wrote: >> Qian Cai <quic_qiancai@xxxxxxxxxxx> writes: >> >>> On Mon, Jun 20, 2022 at 10:20:07PM +0800, Muchun Song wrote: >>>> The lock does not protect the read sides. So the write side should be >>>> fixed by WRITTE_ONCE(). >>> >>> https://lwn.net/Articles/816854/ >>> >>> "Unmarked writes (aligned and up to word size) can be treated as if they had >>> used WRITE_ONCE() by building with >>> CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=y (also selected by default). > > All right, CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC help us avoid KCSAN > complaining. > >>> Experience has shown that compilers are much less likely to destructively >>> optimize in-kernel writes than reads. Some developers might therefore >>> choose to use READ_ONCE() but omit the corresponding WRITE_ONCE(). Other >>> developers might prefer the documentation benefits and long-term peace of >>> mind accruing from explicit use of WRITE_ONCE()..." >> >> Thanks for pointing me to this great article. So although not required >> by KCSAN strictly, WRITE_ONCE() is still good for documentation, etc. >> Just like we have done for swap_info_struct->highest_bit, etc. >> > > +1 I tend to agree with Muchun & Huang, Ying. Thanks all of you. > >> Best Regards, >> Huang, Ying >> > . >
