Re: Further copy_from_user() discussion.

Catalin Marinas
2005-04-15T10:14:49Z

Vadim Lobanov <vlobanov@speakeasy.net> wrote:
> I think I misspoke a bit in my email above. The intent was not to
> eliminate all might_sleep() calls from the copy_from_user() code path;
> but rather juggle the source around a bit so there is only one
> might_sleep() call per each code path. Currently, in the default case,
> it calls it twice.
>
> By the way, is the following still true about might_sleep()?
> http://kerneltrap.org/node/3440/10103

With Ingo's realtime-preempt patch, might_sleep() expands to
might_resched(). The latter expands to cond_resched() only if
CONFIG_PREEMPT_VOLUNTARY is enabled (for CONFIG_PREEMPT_RT this is not
needed since the kernel is involuntarily preemptible). In this case it
might be useful to have might_sleep() only called before memset().

--
Catalin