Commit c000131c authored by Linus Torvalds's avatar Linus Torvalds
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Merge branch 'core-fixes-for-linus' of... 

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
parents 041924ec 8558f8f8

kernel/rcuclassic.c

+15 −1
Original line number Diff line number Diff line
@@ -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);