Re: [PATCH v4 net-next 2/4] net: convert low latency sockets tosched_clock()

From: Eric Dumazet
Date: Thu Jun 13 2013 - 23:13:00 EST

On Fri, 2013-06-14 at 04:57 +0300, Eliezer Tamir wrote:
> Use sched_clock() instead of get_cycles().
> We can use sched_clock() because we don't care much about accuracy.
> Remove the dependency on X86_TSC
> Signed-off-by: Eliezer Tamir <eliezer.tamir@xxxxxxxxxxxxxxx>
> ---

> -static inline bool can_poll_ll(cycles_t end_time)
> +static inline bool can_poll_ll(u64 end_time)
> {
> - return !time_after((unsigned long)get_cycles(),
> + return !time_after((unsigned long)sched_clock(),
> (unsigned long)end_time);
> }

I do not really understand why you bother to have 64bit wide values,
and then use these "unsigned long" casts here.

On 32bit arches, this will really limit to 2^31 ns range.

You should instead either :
- use time_after_64() or
- explicitly limit sysctl_net_ll_poll range

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