[lkml]   [2012]   [Feb]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH RFC tip/core/rcu 39/41] rcu: Wait at least a jiffy before declaring a CPU to be offline
    On Wed, Feb 01, 2012 at 11:41:57AM -0800, Paul E. McKenney wrote:
    > From: "Paul E. McKenney" <>
    > The force_quiescent_state() function uses a state machine to help
    > force grace periods to completion. One of its responsibilities is to
    > detect offline CPUs, and to report quiescent states on their behalf.
    > However, the CPU hotplug process is not atomic, in fact, there is
    > significant uncertainty as to exactly when a given CPU came online or
    > went offline. For example, once a CPU has marked itself offline and
    > executed the CPU_DYING notifiers, it continues executing, entering
    > the scheduler and perhaps also the idle loop.
    > In the old days, force_quiescent_state() was guaranteed to wait for
    > several jiffies before declaring a given CPU offline. This is no
    > longer the case, due to some of the more aggressive rcutorture tests
    > and the CONFIG_RCU_FAST_NO_HZ idle-entry code. Therefore, this commit
    > makes force_quiescent_state() explicitly wait for at least a jiffy
    > before declaring a CPU to be offline.

    This commit seems to implement behavior documented as working in patch
    38. Shouldn't those bits go together?

    - Josh Triplett

     \ /
      Last update: 2012-02-02 07:15    [W:0.024 / U:16.176 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site