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Commit 696a02cc16b182dd78b1f395ae336f449cc90f11

Authored by Paul E. McKenney
Committed by Paul E. McKenney
1 parent c3ce910b14
Exists in smarc-l5.0.0_1.0.0-ga and in 5 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga

rcu: Hold off RCU_FAST_NO_HZ after timer posted 

This commit handles workloads that transition quickly between idle and
non-idle, and where the CPU's callbacks cannot be invoked, but where
RCU does not have anything immediate for the CPU to do.  Without this
patch, the RCU_FAST_NO_HZ code can be invoked repeatedly on each entry
to idle.  The commit sets the per-CPU rcu_dyntick_holdoff variable to
hold off further attempts for a tick.

Reported-by: "Abou Gazala, Neven M" <neven.m.abou.gazala@intel.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Showing 1 changed file with 1 additions and 1 deletions Side-by-side Diff

kernel/rcutree_plugin.h
Diff comments   View file @ 696a02c
... ... @@ -2138,7 +2138,7 @@
2138 2138 /* Can we go dyntick-idle despite still having callbacks? */
2139 2139 trace_rcu_prep_idle("Dyntick with callbacks");
2140 2140 per_cpu(rcu_dyntick_drain, cpu) = 0;
2141   - per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
  2141 + per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
2142 2142 if (rcu_cpu_has_nonlazy_callbacks(cpu))
2143 2143 hrtimer_start(&per_cpu(rcu_idle_gp_timer, cpu),
2144 2144 rcu_idle_gp_wait, HRTIMER_MODE_REL);