01a8133034
In theory, synchronize_sched() requires a read-side critical section to order against. In practice, preemption can be thought of as being disabled across every machine instruction, at least for those machine instructions that are not in the idle loop and not on offline CPUs. So this commit removes the redundant preempt_disable() from rcu_note_voluntary_context_switch(). Please note that the single instruction in question is the store of zero to ->rcu_tasks_holdout. The "if" is simply a performance optimization that avoids unnecessary stores. To see this, keep in mind that both the "if" condition and the store are in a quiescent state. Therefore, even if the task is preempted for a full grace period (presumably due to its having done a context switch beforehand), the store will be recording a legitimate quiescent state. Reported-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Conflicts: include/linux/rcupdate.h |
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| acpi | ||
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| clocksource | ||
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| keys | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
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| ras | ||
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| sound | ||
| target | ||
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| uapi | ||
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| xen | ||
| Kbuild | ||