X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=kernel%2Frcuclassic.c;h=a38895a5b8e2eeb1da28a829bebfe4a963c97561;hb=9ad4107ba137f743fc531f9f4ceb81b122f9ff25;hp=f4ffbd0f306f57c63afbe502c235df1b5e8548ed;hpb=29bd17af7d8ffc16bb5eb286947495c166ea826e;p=linux-2.6

diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index f4ffbd0f30..a38895a5b8 100644
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -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);