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sched: Remove synchronize rcu/sched calls from _cpu_down

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There is no need for sync_sched() in _cpu_down as stop_machine()
provides that barrier implicitly. Removing it also helps improve
hot-unplug latency.

The sync_sched/rcu were earlier removed for the same reason by the
commit 9ee349ad6d ("sched: Fix set_cpu_active() in cpu_down()"),
but recently got added as part of commit <6acce3ef84520537> ("sched:
Remove get_online_cpus() usage.").

CRs-Fixed: 1048941
Change-Id: I97763004454d082d3cc2d9d9dbef7da923608600
Signed-off-by: Kaushal Kumar <kaushalk@codeaurora.org>
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>
Signed-off-by: Runmin Wang <runminw@codeaurora.org>
This commit is contained in:
Kaushal Kumar 2014-05-15 19:19:04 +05:30 • committed by Runmin Wang
parent 2566204c8d
commit 36131fdc87
1 changed files with 0 additions and 15 deletions
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15
kernel/cpu.c
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@ -365,21 +365,6 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen)
goto out_release;
}
/*
* By now we've cleared cpu_active_mask, wait for all preempt-disabled
* and RCU users of this state to go away such that all new such users
* will observe it.
*
* For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
* not imply sync_sched(), so wait for both.
*
* Do sync before park smpboot threads to take care the rcu boost case.
*/
if (IS_ENABLED(CONFIG_PREEMPT))
synchronize_rcu_mult(call_rcu, call_rcu_sched);
else
synchronize_rcu();
smpboot_park_threads(cpu);
/*