lkml.org 
[lkml]   [2014]   [Jul]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH 09/16] rcu: Remove redundant check for online cpu
    On Wed, Jul 23, 2014 at 11:30 AM, Paul E. McKenney
    <paulmck@linux.vnet.ibm.com> wrote:
    > On Wed, Jul 23, 2014 at 11:11:45AM -0400, Pranith Kumar wrote:
    >> On Wed, Jul 23, 2014 at 10:23 AM, Paul E. McKenney
    >> <paulmck@linux.vnet.ibm.com> wrote:
    >> > On Wed, Jul 23, 2014 at 10:12:54AM -0400, Pranith Kumar wrote:
    >> >> On Wed, Jul 23, 2014 at 9:50 AM, Paul E. McKenney
    >> >> <paulmck@linux.vnet.ibm.com> wrote:
    >> >> > On Wed, Jul 23, 2014 at 08:59:06AM -0400, Pranith Kumar wrote:
    >> >> >> On Wed, Jul 23, 2014 at 8:21 AM, Paul E. McKenney
    >> >> >> <paulmck@linux.vnet.ibm.com> wrote:
    >> >> >> > On Wed, Jul 23, 2014 at 01:09:46AM -0400, Pranith Kumar wrote:
    >> >> >> >> There are two checks for an online CPU if two if() conditions. This commit
    >> >> >> >> simplies this by replacing it with only one check for the online CPU.
    >> >> >> >>
    >> >> >> >> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
    >> >> >> >
    >> >> >> > I admit that it is very early in the morning my time, but I don't see
    >> >> >> > this change as preserving the semantics in all cases. Please recheck
    >> >> >> > your changes to the second check.
    >> >> >> >
    >> >> >> > Thanx, Paul
    >> >> >>
    >> >> >> I guess you must be thrown off by the complementary checks, the first
    >> >> >> check is for cpu_online() and second is for cpu_is_offline(). :)
    >> >> >>
    >> >> >> Previously, if a cpu is offline, the first condition is false and the
    >> >> >> second condition is true, so we return from the second if() condition.
    >> >> >> The same semantics are being preserved.
    >> >> >
    >> >> > Fair enough!
    >> >> >
    >> >> > Nevertheless, I am not seeing this as a simplification.
    >> >>
    >> >> I am not sure what you mean here, do you mean that both the checks are
    >> >> actually required?
    >> >
    >> > I mean that the current compound tests each mean something. Pulling out
    >> > the offline test adds lines of code and obscures that meaning. This means
    >> > that it is easier (for me, anyway) to see why the current code is correct
    >> > than it is to see why your suggested change is correct.
    >> >
    >>
    >> That is a valid point. I did not mean to reduce readability of the
    >> code. Just trying to avoid the overhead of smp_processor_id().
    >>
    >> Not sure if you would prefer this, but how about the following?
    >
    > If you change the "awake" to something like "am_online", I could get
    > behind this one.
    >

    OK! I will submit that in the next series(with the zalloc check).

    --
    Pranith


    \
     
     \ /
      Last update: 2014-07-24 09:03    [W:4.226 / U:0.824 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site