Messages in this thread |  | | Subject | Re: [PATCH 7/7] xen/evtchn: read producer index only once | From | Julien Grall <> | Date | Mon, 8 Feb 2021 11:50:58 +0000 |
| |
On 08/02/2021 10:59, Jürgen Groß wrote: > On 08.02.21 11:51, Jan Beulich wrote: > Yes, but I don't see an urgent need to fix that, as there would > be thousands of accesses in the kernel needing a fix. A compiler > tearing a naturally aligned access into multiple memory accesses > would be rejected as buggy from the kernel community IMO.
I would not be so sure. From lwn [1]:
"In the Linux kernel, tearing of plain C-language loads has been observed even given properly aligned and machine-word-sized loads.)"
And for store tearing:
"Note that this tearing can happen even on properly aligned and machine-word-sized accesses, and in this particular case, even for volatile stores. Some might argue that this behavior constitutes a bug in the compiler, but either way it illustrates the perceived value of store tearing from a compiler-writer viewpoint. [...] But for properly aligned machine-sized stores, WRITE_ONCE() will prevent store tearing."
Cheers,
[1] https://lwn.net/Articles/793253/#Load%20Tearing
> > > Juergen
-- Julien Grall
|  |