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Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 

* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  rcu: fix hotplug vs rcu race
This commit is contained in:
Linus Torvalds 2008-07-02 18:59:45 -07:00
parent 041924ec2f 8558f8f816
commit c000131c71
1 changed files with 15 additions and 1 deletions
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16
kernel/rcuclassic.c
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@ -89,8 +89,22 @@ static void force_quiescent_state(struct rcu_data *rdp,
/*
* Don't send IPI to itself. With irqs disabled,
* rdp->cpu is the current cpu.
*
* cpu_online_map is updated by the _cpu_down()
* using stop_machine_run(). Since we're in irqs disabled
* section, stop_machine_run() is not exectuting, hence
* the cpu_online_map is stable.
*
* However, a cpu might have been offlined _just_ before
* we disabled irqs while entering here.
* And rcu subsystem might not yet have handled the CPU_DEAD
* notification, leading to the offlined cpu's bit
* being set in the rcp->cpumask.
*
* Hence cpumask = (rcp->cpumask & cpu_online_map) to prevent
* sending smp_reschedule() to an offlined CPU.
*/
cpumask = rcp->cpumask;
cpus_and(cpumask, rcp->cpumask, cpu_online_map);
cpu_clear(rdp->cpu, cpumask);
for_each_cpu_mask(cpu, cpumask)
smp_send_reschedule(cpu);