On Wed, 17 Jan 2018, Lingutla Chandrasekhar wrote:
> In case when timers are migrated to a CPU, after it exits
> idle, but before timer base is forwarded, either from
> run_timer_softirq()/mod_timer()/add_timer_on(), it's
> possible that migrated timers are queued, based on older
> clock value. This can cause delays in handling those timers.
>
> For example, consider below sequence of events:
>
> - CPU0 timer1 expires = 59969 and base->clk = 59131. So,
> timer is queued at level 2, with next expiry for this timer
> = 60032 (due to granularity addition).
> - CPU1 enters idle @60007, with next timer expiry @60020.
> - CPU1 exits idle.
> - CPU0 is hotplugged at 60009, and timers are migrated to
> CPU1, with new base->clk = 60007. timer1 is queued,
> based on 60007 at level 0, for immediate handling (in
> next timer softirq handling).
> - CPU1's base->clk is forwarded to 60009, so, in next sched
> timer interrupt, timer1 is not handled.
>
> The issue happens as timer wheel collects expired timers
> starting from the current clk's index onwards, but migrated
> timers, if enqueued, based on older clk value can result
> in their index being less than clk's current index.
> This can only happen if new base->clk is ahead of
> timer->expires, resulting in timer being queued at
> new base->clk's current index.
>
> Signed-off-by: Lingutla Chandrasekhar <clingutla@xxxxxxxxxxxxxx>
> Signed-off-by: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
That's still wrong.
The SOB chain should be:
SOB: Author
SOB: Handler/Transporter
SOB: Committer
So if you wrote te patch then Neeraj's SOB is wrong. If Neeraj wrote the
patch then the patch should contain a
From: Neeraj
line right at the top of the changelog.
If you both developed the patch then please use;
Co-developed-by: Neeraj
Signed-off-by: Neeraj
Signed-off-by; You
That would make you the Author in the git commit, but still preserve the
co-authorship.
Please clarify what applies to this particular patch.
Thanks,
tglx
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