9 Aug
2019
9 Aug
'19
12:49 p.m.
Quoting Lionel Landwerlin (2019-08-09 13:38:57)
On 09/08/2019 14:58, Chris Wilson wrote:
Not atomic (the u64 write should really be to avoid total corruption) and nothing prevents userspace from racing. How safe is that in the overall design?
Atomic would prevent issue related to 2 processes/threads seeing different values because of caching?
No, the kernel atomics themselves do not guarantee memory barriers in all cases. The issue I see here is that we can not safely do a u64 increment on all platforms without write tearing. E.g. two clients simultaneously incrementing from U32_MAX becomes 0x1 (both would report U32_MAX) -Chris